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First published online April 17, 2003; 10.1104/pp.102.017145 Plant Physiology 132:757-767 (2003) © 2003 American Society of Plant Biologists Arabidopsis hot Mutants Define Multiple Functions Required for Acclimation to High Temperatures1Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, Arizona 85721
Plants acquire thermotolerance to lethal high temperatures if first exposed to moderately high temperature or if temperature is increased gradually to an otherwise lethal temperature. We have taken a genetic approach to dissecting acquired thermotolerance by characterizing loss-of-function thermotolerance mutants in Arabidopsis. In previous work, we identified single recessive alleles of four loci required for thermotolerance of hypocotyl elongation, hot1-1, hot2-1, hot3-1, and hot4-1. Completed screening of M2 progeny from approximately 2500 M1 plants has now identified new alleles of three of these original loci, along with three new loci. The low mutant frequency suggests that a relatively small number of genes make a major contribution to this phenotype or that other thermotolerance genes encode essential or redundant functions. Further analysis of the original four loci was performed to define the nature of their thermotolerance defects. Although the HOT1 locus was shown previously to encode a major heat shock protein (Hsp), Hsp101, chromosomal map positions indicate that HOT2, 3, and 4 do not correspond to major Hsp or heat shock transcription factor genes. Measurement of thermotolerance at different growth stages reveals that the mutants have growth stage-specific heat sensitivity. Analysis of Hsp accumulation shows that hot2 and hot4 produce normal levels of Hsps, whereas hot3 shows reduced accumulation. Thermotolerance of luciferase activity and of ion leakage also varies in the mutants. These data provide the first direct genetic evidence, to our knowledge, that distinct functions, independent of Hsp synthesis, are required for thermotolerance, including protection of membrane integrity and recovery of protein activity/synthesis.
Plants have many different mechanisms for surviving high temperatures in their environment, including long-term evolutionary adaptations of life history and morphology and shorter term avoidance or acclimation mechanisms involving, for example, leaf orientation, transpirational cooling, or alterations of membrane lipid composition (Berry, 1975  ; Turner and Kramer, 1980; Radin et al., 1994). It has also long been known that plants, like other organisms, have the ability to acquire thermotolerance rapidly, within hours, to otherwise normally lethal high temperatures (Alexandrov, 1961; Lin et al., 1984; Neumann et al., 1989; Vierling, 1991). The acquisition of thermotolerance is a cell autonomous phenomenon and results from prior exposure to a conditioning pretreatment, which can be a short, sublethal high temperature or other moderate stress treatments (Lindquist, 1986). Thermotolerance can also be induced by a gradual increase to the normally lethal temperature (Vierling, 1991), as would be experienced in the natural environment (Ansari and Loomis, 1959; Ehler, 1973). Even plants growing in their natural distribution range may experience high temperatures that would be lethal in the absence of this rapid acclimation; thus, ability to acquire thermotolerance is likely of significant importance to plants. Furthermore, because plants can experience major diurnal temperature fluctuations, the acquisition of thermotolerance may reflect a more general mechanism that contributes to homeostasis of metabolism on a daily basis.
Although acquired thermotolerance has been described and studied in plants for decades (Alexandrov, 1994
Even if all Hsps contribute to thermotolerance, it is highly likely that other factors are also necessary. In addition to causing protein denaturation, high temperature also alters membrane fluidity, can disrupt the overall balance of metabolic processes, and leads to oxidative stress (Dewey, 1989
We have taken a genetic approach to dissecting the mechanism of acquired thermotolerance and have reported the isolation of four recessive, nonallelic mutations (hot1 to 4) in Arabidopsis that are defective in acquired thermotolerance of hypocotyl elongation (Hong and Vierling, 2000
Isolation of New hot Mutants
We previously described recessive, ethyl methanesulfonate (EMS) mutations at four independent loci, HOT1 to 4, that fail to develop thermotolerance in response to moderate heat treatment (Hong and Vierling, 2000 Isolating second alleles of three of the original hot mutants in this mutant population is consistent with the conclusion that a relatively small number of genes make strong contributions to the hypocotyl thermotolerance phenotype or that mutation of other functions must be lethal or redundant. The low mutant frequency and isolation of multiple alleles also indicates that the hot mutants are unlikely to represent random temperature-sensitive mutations in any gene but rather are specific to the mechanism of acquired thermotolerance. Further work reported here was performed with the original set of alleles (hot1-1, hot2-1, hot3-1, and hot4-1) after a single backcross to the wild-type Columbia parent, and the new alleles were tested (before backcrossing) in many of the assays, as discussed in the text. Further genetic and phenotypic characterization of the newly isolated mutants is continuing.
To begin to establish the identity of the hot2, hot3, and hot4 mutations, their chromosomal map positions were determined as shown in Figure 1 (see "Materials and Methods"). The HOT1 gene was mapped to bacterial artificial chromosome F9E11 and identified as Hsp101 as described previously (Hong and Vierling, 2000
To determine if the hot mutations have strong effects on growth and development under optimal conditions, the mutants were observed through a complete life cycle. As documented in Figure 2, only the hot2-1 mutant showed consistent phenotypes significantly different from wild type. The hot2-1 plants are semidwarf and highly branched. The semidwarf phenotype of hot2-1 is also seen in hypocotyl length (see Fig. 3). These phenotypes were also observed in hot2-2 and segregated with the hypocotyl thermotolerance defect as judged from observations of approximately 600 seedlings and over 300 mature plants.
The hot mutants were all isolated based on their failure to show acquired thermotolerance in a hypocotyl elongation assay (Hong and Vierling, 2000 In contrast to the small quantitative differences between the mutants in the hypocotyl assay, the ability of 10-d-old seedlings to acquire thermotolerance differed dramatically between the mutants (Fig. 3B). The hot1-1 and hot2-1 mutants failed to acquire thermotolerance at this stage; they ceased production of additional leaves and existing leaves and cotyledons turned white. In the same assay, hot3-1 and hot4-1 behaved like wild type. In fact, hot4-1 consistently appeared more robust than wild type after either a 38°C pretreatment alone (not shown) or after the pretreatment followed by a 45°C stress (Fig. 3B). Again, results with the other alleles were the same (not shown), arguing that this stage specificity of thermotolerance is gene specific.
Before germination, imbibed Arabidopsis seeds have greater temperature tolerance than seedlings. That is, without any acclimating pretreatment, imbibed seeds can be heated at 45°C for at least 150 min and still survive and grow (Hong and Vierling, 2000
Another phenotype that can be scored for the development of thermotolerance is the ability of dark-grown seedlings to accumulate chlorophyll (develop chloroplasts). In this assay, which has been used by Burke et al. (2000
Because the expression of Hsp101 is essential for thermotolerance, and expression of other Hsps is likely to also be essential, the level of Hsp101 and selected sHsps was estimated by western analysis in the hot mutants as shown in Figure 4. In all of the mutants, the Hsps were not present at significant levels before heat stress. Accumulation of Hsps after the 38°C conditioning pretreatment in 2.5- and 10-d-old seedlings revealed a wild-type pattern of expression in hot1-1, as seen previously (Hong and Vierling, 2000
To investigate further the decreased expression of Hsp101 in hot3-1, a 40°C 90-min treatment, rather than a 38°C treatment, was used to induce Hsp accumulation in 2- or 10-d-old seedlings. At this increased temperature, the induction of all Hsps tested was significantly reduced in hot3-1 (Fig. 4), whereas induction remained unchanged in all the other genotypes. Analysis of a dilution series (not shown) indicates that Hsp101 and class II sHsps (Hsp17.6II) are reduced by 50%, and class I sHsps (Hsp17.4) are reduced by about 70%. Thus, the defect in hot3-1 is not restricted to the expression of Hsp101, but has a more general effect on accumulation of Hsps that is more severe at higher temperatures. When 10-d-old seedlings given the 40°C pretreatment were examined for acquired thermotolerance to a 45°C treatment, hot3-1 was now found to be unable to acquire tolerance, similar to hot1-1 and hot2-1, whereas wild-type and hot4-1 seedlings still exhibited thermotolerance as before (not shown). The reduced thermotolerance of hot3-1 under these treatment conditions may be related to the greater reduction in Hsp induction.
Hsp levels were also tested in seeds, which are known to store significant levels of Hsp101 and specific class I and class II cytosolic sHsps (Wehmeyer et al., 1996
In total, results of the above thermotolerance tests indicate that each of the hot mutants must be defective in different processes required for the development of thermotolerance. To begin to dissect the thermotolerance mechanism, assays that measure biochemical functions, rather than only survival and growth, were necessary. For this purpose, an assay for the heat tolerance of a reporter enzyme, firefly luciferase (Luc), was developed. Luc is a very thermolabile protein that has been used extensively both in vitro and in vivo to examine the effects of heat treatment and the mechanism of chaperone action (Pinto et al., 1991 The results in Figure 5 demonstrate that pretreatment of 7-d-old seedlings at 38°C has little effect on Luc activity in any of the mutants, whereas subsequent treatment at 45°C reduced activity basically to zero in wild type and all of the mutants. However, Luc activity begins to recover within 3 h after 45°C treatment in wild type and is essentially fully recovered after 24 h. In comparison, the hot1-1 and hot3-1 mutants show dramatically reduced ability to recover Luc activity, with hot1-1 exhibiting the most severe phenotype. The phenotype of hot3-1, which is delayed in recovery but still shows significant recovery after 24 h, is consistent with the observation that thermotolerance of 10-d-old hot3-1 seedlings pretreated at 38°C appears similar to wild type as assessed by growth 5 d after heat stress (Fig. 3B). The hot2-1 mutant recovers Luc activity as rapidly as wild type, despite the fact that hot2-1 seedlings are severely damaged or die from the treatment (Fig. 3). Luc activity in hot4-1 actually achieves higher levels after 24 h of recovery than what is seen for wild type.
Wild-type Luc activity in hot4-1 could reflect the absence of a thermotolerance defect in hot4-1 mutants at this growth stage (see Fig. 3B). To test if Luc activity in hot4-1 was compromised in 2-d-old heat-treated seedlings, Luc activity was also monitored in the mutants under the conditions used for the hypocotyl elongation assay. Even at this growth stage, where hypocotyl elongation is blocked by heat stress, Luc activity recovered as well or better than in wild type in hot4-1, and results with the other mutants were also similar to the those seen with 10-d-old seedlings (not shown). The Luc reaction requires ATP and, therefore, is expected to be sensitive to intracellular ATP concentrations. To confirm that the in vivo luminescence measurements reflect the level of active Luc rather than the level of intracellular ATP, selected samples were also extracted for analysis of Luc activity in vitro with added ATP (see "Materials and Methods"). Extractable Luc activity paralleled the activity assessed by in vivo imaging (not shown), indicating the in vivo measurements are a valid measure of Luc activity, rather than a measure of ATP levels. In total, these data indicate that ability to recover Luc activity, which could reflect ability to reactivate denatured enzyme or to recover normal transcriptional and translational activities, is necessary (hot1-1 and hot3-1) but not sufficient (hot2-1 and hot4-1) for the development of thermotolerance.
Heat is also predicted to alter membrane transport properties, possibly through effects on membrane fluidity or the activity of membrane channels and transporters (Levitt, 1980
Our analysis of loss-of-function mutants in Arabidopsis has defined seven loci, the HOT genes, required for the acquisition of thermotolerance. Four of these hot mutations have been mapped to the Arabidopsis genome and exhibit differences in thermotolerance at different life stages. Analysis of biochemical phenotypes of hot1, hot2, hot3, and hot4, including production of Hsps, and thermotolerance of Luc activity and of ion leakage provide the first direct genetic evidence that at least four distinct functions are required for thermotolerance. These include production of Hsps, specifically Hsp101, protection of membrane integrity, recovery of protein activity/synthesis, and at least one other undefined function. Disruption of any one of these functions is sufficient to eliminate the ability of plants to acclimate to high temperature, underscoring the fact that engineering increased plant heat tolerance will require manipulation of multiple cellular characteristics.
We have considered the possibility that temperature-sensitive mutations in any gene could lead to a loss-of-thermotolerance phenotype that is unrelated to the mechanism of acquired thermotolerance. However, several lines of evidence indicate that the hot mutations represent specific lesions affecting functions required for thermotolerance, rather than unrelated temperature-sensitive mutations. First, the conditions under which the hot mutations reveal their phenotype are short-term high-temperature treatments, as opposed to continuous growth at elevated temperatures, as is typically used for identification of temperature-sensitive mutations. It seems unlikely that a brief period at 45°C, but not 38°C, would irreversibly inactivate all of these proteins and that their function could not be replaced by new protein synthesis during the recovery period. Second, our screen identified the Hsp101 gene (HOT1), which had been established previously in bacteria and yeast (Saccharomyces cerevisiae) as essential for acquired thermotolerance (Schirmer et al., 1996 The stage-specific effects on seed, 2.5-, and 10-d-old seedling thermotolerance in the hot mutants are quite striking. Although all the mutants are defective in acquired thermotolerance of hypocotyl elongation, only hot1 is defective in all three growth assays. These data, along with the hot1 defect in thermotolerance of chlorophyll accumulation and Luc recovery, emphasize that many processes are dependent on the function of this single chaperone protein. The ability of the hot4 mutants to acquire thermotolerance after 10 d, but not 2.5 d of growth, might be explained by activation of redundant stress recovery pathways during seedling growth.
As shown previously, the hot1 mutations demonstrate that production of a specific Hsp, Hsp101, is required for thermotolerance (Hong and Vierling, 2000
The hot2 and hot4 mutations unambiguously demonstrate that functions independent of Hsp101, Hsp70, and sHsps are required for thermotolerance. These mutants produce normal levels of Hsp101 and sHsps despite their failure to develop thermotolerance. Map positions of the hot2 and hot4 mutations also fall outside intervals containing Hsp70 or other sHsp genes. It remains highly possible that induction of Hsp70 and sHsps are both critical to thermotolerance, as implicated in other studies (Waters et al., 1996
The phenotype of the hot2-1 mutant provides evidence that modulation of membrane properties is an essential aspect of acquired thermotolerance. The hot2-1 mutant shows reproducibly higher levels of electrolyte leakage compared with wild-type plants under control conditions, and increased electrolyte leakage at 45°C is not protected by a pretreatment at 38°C as it is in wild type and the other hot mutants. Lin et al. (1985 The hot3-1 mutation clearly affects accumulation of Hsp101 and sHsps, with the defect increasing at higher temperatures. The reduced level of Hsp101 could account for the slow recovery of Luc activity in 2.5- and 10-d-old seedlings of this mutant. However, it seems unlikely that decreased synthesis of Hsp101 is solely responsible for the thermotolerance defect of hot3. In 2.5-d-old seedlings, at least 50% wild-type levels of Hsp101 are produced, which appear sufficient for thermotolerance as demonstrated in Hsp101 antisense experiments (Queitsch et al., 2000). Furthermore, a similar reduction in Hsp101 accumulation occurred in 10-d-old plants pretreated at 38°C, and these plants showed normal acquisition of thermotolerance. Only when pretreatment was increased to 40°C was acquired thermotolerance lost in hot3-1, in parallel with reduced expression of additional Hsps. Rather then interpreting the failure of Luc recovery as arising from decreased Hsps, it is also possible that reduced Hsps and reduced Luc recovery are caused by the same defect, such as a failure of some aspect of transcription or translation in hot3-1. Both transcriptional and translational activities have been shown to acquire thermotolerance. At this time, it is difficult to interpret further the phenotype of hot4. This mutant showed normal Hsp synthesis, Luc recovery, and adaptation of electrolyte leakage. It also acquired full thermotolerance as 10-d-old seedlings and showed no difference in basal thermotolerance of seeds. Thus, the only thermotolerance phenotype yet identified in hot4 is restricted to acquired thermotolerance of hypocotyl elongation. In fact, despite the obvious sensitivity of 2.5-d-old seedlings, we reproducibly observe 10-d-old hot4-1 seedlings perform much better than wild type after heat stress. Further assays are required to determine what defects underlie growth arrest at the hypocotyl stage after heat treatment of hot4. Cloning the different HOT genes will provide new insight into mechanisms essential for acquired thermotolerance. Equally of interest is to use the hot mutants to investigate if any of the same genes are involved in tolerance to chronic heat stress or to other forms of abiotic stress. The screen in which the hot mutants were identified is unlikely to identify many more genes. Additional genes are no doubt required for thermotolerance but are either redundant, or stage specific in function, or would result in lethality in a thermotolerance screen. Using the hot mutations to isolate enhancer and suppressor mutations will provide a further genetic approach to dissecting thermotolerance.
Plant Growth Conditions Arabidopsis ecotypes Columbia and No were used where indicated. Plants were grown in lighted growth chambers (approximately 100 µmol m–2 s–1) on a 22°C/18°C, 16-h day/night cycle. All seeds used for testing thermotolerance and Hsp levels during seed development were derived from plants grown under these controlled conditions.
Genetic complementation tests and analysis of dominance were performed as described previously, using the hypocotyl assay of thermotolerance (Hong and Vierling, 2000
For genetic mapping, the hot2, hot3, and hot 4 mutants were outcrossed with wild-type plants of the Landsberg erecta ecotype. The resulting F1 plants were allowed to self, and homozygous hot mutants in the segregating F2 population were selected on the basis of their phenotype in the hypocotyl thermotolerance assay. Genomic DNA was extracted according to Klimyuk et al. (1993
Thermotolerance assays of seeds, 2.5-d dark-grown and 10-d-old light-grown seedlings were performed basically according to Hong and Vierling (2000
Total protein from seed or seedlings was extracted in SDS sample buffer (60 mM Tris-HCl [pH 8.0], 60 mM dithiothreitol, 2.0% [w/v] SDS, 15% [w/v] Suc, 5 mM
Standard methods were used for SDS-PAGE separation of protein samples on 7.5% or 15% (w/v) polyacrylamide gels. For western analysis, proteins were blotted to nitrocellulose and processed for detection using chemiluminescence (Amersham, Piscataway, NJ) as described previously (Wehmeyer et al., 1996
To measure ion leakage caused by high temperature, 10-d-old light-grown seedlings were removed from the plates after different treatments, rinsed briefly with deionized water, and immediately placed in a tube with 5 mL of deionized water. The tubes were placed at 22°C overnight before conductivity was measured using an Electroconductivity Meter (model 1054, VWR Scientific, Phoenix). Results represent the average from measurements of ten seedlings for each condition.
Seven-day-old light-grown seedlings were used to measure the recovery of Luc activity after heat shock. Seedlings were pretreated at 38°C, allowed to recover for 2 h at 22°C, and then heat shocked at 45°C for 2 h. For luminescence imaging, plants were sprayed uniformly with 1.0 mM luciferin in 0.01% (v/v) Triton X-100 at different times and kept in the dark for 10 min before imaging. All images were obtained with 5 min of exposure time on a CCD camera system (Roper Scientific, Princeton). The luminescence intensity of each seedling was quantified with WinView software system (Roper Scientific).
Luc activity in plant extracts was determined in parallel to the in vivo luminescence measurements. Samples were prepared from control seedlings, seedlings pretreated for 90 min at 38°C, and seedlings after 1, 6, or 24 h of recovery from 45°C heat stress. Seedlings were homogenized with 50 µL of extraction buffer containing 100 mM K2HPO4/KH2PO4 (pH 7.8), 1.0 mM dithiothreitol, 1.0 mM benzamidine, and 5 mM
We would like to thank Nicole Buan for her work to produce Arabidopsis class II sHsp antibodies, Dr. Judy Callis for her gift of the UBQ10::Luc transgenic plants, Dr. Jian-Kang Zhu for use of his imaging facilities, and Dr. John Burke and his laboratory for performing assays of the thermotolerance of chlorophyll accumulation. We also thank Chris Borchert, Sarah Ryan, and Shannon Parrington for help with planting and screening of Arabidopsis seedlings. Drs. Frans Tax and Ramin Yadegari provided helpful comments on this manuscript. Received November 5, 2002; returned for revision December 10, 2002; accepted December 10, 2002.
Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.102.017145.
1 This work was supported by the U.S. Department of Agriculture (National Research Initiative Competitive Grants Program grant no. 99–35100–7618) and by the Department of Energy (Energy Biosciences grant no. DE–FG03–99ER20338) to E.V.
2 Present address: Chonnam National University, 300 Yongbongdong, Buk-gu, Gwangju 500–757, Korea. * Corresponding author; e-mail vierling{at}u.arizona.edu; fax 520–621–1601.
Alexandrov V (1964) Cytophysiological and cytoecological investigations of heat resistance of plant cells toward the action of high and low temperature. Q Rev Biol 39: 35–77 Alexandrov V (1994) Functional aspects of cell response to heat shock. Int Rev Cytol 148: 171–227[Medline] Ansari AQ, Loomis WE (1959) Leaf temperatures. Am J Bot 46: 713–717[CrossRef][Web of Science]
Berry JA (1975) Adaptation of photosynthetic processes to stress. Science 188: 644–650 Boston RS, Viitanen PV, Vierling E (1996) Molecular chaperones and protein folding in plants. Plant Mol Biol 32: 191–222[CrossRef][Web of Science][Medline] Buchberger A, Schröder H, Hesterkamp T, Schönfeld HJ, Bukau B (1996) Substrate shuttling between the DnaK and GroEL systems indicates a chaperone network promoting protein folding. J Mol Biol 261: 328–333[CrossRef][Web of Science][Medline] Burke JJ (2001) Identification of genetic diversity and mutations in higher plant acquired thermotolerance. Physiol Plant 112: 167–170[CrossRef]
Burke JJ, O'Mahony PJ, Oliver MJ (2000) Isolation of Arabidopsis mutants lacking components of acquired thermotolerance. Plant Physiol 123: 575–587 Dewey WC (1989) The search for critical cellular targets damaged by heat. Radiat Res 120: 191–204[Medline]
Ehler WL (1973) Cotton leaf temperatures as related to soil water depletion and meteorological factors. Agron J 65: 404–409 Forreiter C, Kirschner M, Nover L (1997) Stable transformation of an Arabidopsis cell suspension culture with firefly luciferase providing a cellular system for analysis of chaperone activity in vivo. Plant Cell 9: 2171–2181[Abstract] Gething M-J (1997) Guidebook to Molecular Chaperones and Protein Folding Catalysts. Oxford University Press, New York, pp 1–554 Ghosh S, Hepstein S, Heikkila J, Dumbroff E (1988) Use of a densitometer or ELISA plate reader for measurement of nanogram amounts of proteins in crude extracts from biological tissues. Anal Biochem 169: 227–233[CrossRef][Web of Science][Medline] Glover JR, Lindquist S (1998) Hsp104, Hsp70, and Hsp40: A novel chaperone system that rescues previously aggregated proteins. Cell 94: 73–82[CrossRef][Web of Science][Medline] Haughn GW, Somerville C (1986) Sulfonylurea-resistant mutants of Arabidopsis thaliana. Mol Gen Genet 204: 430–434[CrossRef][Web of Science] Hendrick JP, Hartl F-U (1993) Molecular chaperone functions of heat-shock proteins. Annu Rev Biochem 62: 349–384[CrossRef][Web of Science][Medline]
Hong SW, Vierling E (2000) Mutants of Arabidopsis thaliana defective in the acquisition of tolerance to high temperature stress. Proc Natl Acad Sci USA 97: 4392–4397 Hong SW, Vierling E (2001) Hsp101 is necessary for heat tolerance but dispensable for development and germination in the absence of stress. Plant J 27: 25–35[CrossRef][Web of Science][Medline] Klimyuk VI, Carroll BJ, Thomas CM, Jones JDG (1993) Alkali treatment for rapid preparation of plant material for reliable PCR analysis. Plant J 3: 493–494[CrossRef][Web of Science][Medline]
Larkindale J, Knight MR (2002) Protection against heat stress-induced oxidative damage in Arabidopsis involves calcium, abscisic acid, ethylene, and salicylic acid. Plant Physiol 128: 682–695
Lee GJ, Vierling E (2000) A small heat shock protein cooperates with heat shock protein 70 systems to reactivate a heat-denatured protein. Plant Physiol 122: 189–197 Levitt J (1980) Responses of Plants to Environmental Stresses. Academic Press, New York
Lin C-Y, Chen,Y-M, Key JL (1985) Solute leakage in soybean seedlings under various heat shock regimes. Plant Cell Physiol 26: 1493–1498
Lin C-Y, Roberts J, Key JL (1984) Acquisition of thermotolerance in soybean seedlings: synthesis and accumulation of heat shock proteins and their cellular localization. Plant Physiol 74: 152–160 Lindquist S (1986) The heat shock response. Annu Rev Biochem 45: 39–72[CrossRef] Malik MK, Slovin JP, Hwan CH, Zimmerman JL (1999) Modified expression of a carrot small heat shock protein gene, Hsp17.7, results in increased or decreased thermotolerance. Plant J 20: 89–99[CrossRef][Web of Science][Medline]
Michels AA, Kanon B, Konings AWT, Ohtsuka K, Bensaude O, Kampinga HH (1997) Hsp70 and Hsp40 chaperone activities in the cytoplasm and the nucleus of mammalian cells. J Biol Chem 272: 33283–33289 Mogk A, Tomoyasu T, Goloubinoff P, Rüdiger S, Röder D, Langen H, Bukau B (1999) Identification of thermolabile Escherichia coli proteins: prevention and reversion of aggregation by DnaK and ClpB. EMBO J 18: 6934–6949[CrossRef][Web of Science][Medline]
Motohashi K, Watanabe Y, Yohda M, Yoshida M (1999) Heat-inactivated proteins are rescued by the DnaK.J-GrpE set and ClpB chaperones. Proc Natl Acad Sci USA 96: 7184–7189 Neumann D, Nover L, Parthier B, Rieger R, Scharf K-D, Wollgiehn R, Nieden UZ (1989) Heat shock and other stress response systems of plants. Biol Zentbl 108: 1–156
Neuwald AF, Aravind L, Spouge JL, Koonin EV (1999) AAA+: a class of chaperone-like ATPases associated with the assembly, operation, and disassembly of protein complexes. Genome Res 9: 27–43 Nover L, Bharti K, Döring P, Mishra SK, Ganguli A, Scharf K-D (2001) Arabidopsis and the heat stress transcription factor world: how many heat stress transcription factors do we need? Cell Stress Chaperones 6: 177–189[Web of Science][Medline] Parsell DA, Kowal AS, Singer MA, Lindquist S (1994) Protein disaggregation mediated by heat-shock protein Hsp104. Nature 372: 475–478[CrossRef][Medline]
Pinto M, Morange M, Bensaude O (1991) Denaturation of proteins during heat shock: in vivo recovery of solubility and activity of reporter enzymes. J Biol Chem 266: 13941–13946
Radin JW, Lu Z, Percy RG, Zeiger E (1994) Genetic variability for stomatal conductance in Pima cotton and its relation to improvements of heat adaptation. Proc Natl Acad Sci USA 91: 7217–7221
Scharf K-D, Siddique M, Vierling E (2001) The expanding family of small Hsps and other proteins containing an Schirmer EC, Glover JR, Singer MA, Lindquist S (1996) HSP100/Clp proteins: a common mechanism explains diverse functions. Trends Biochem Sci 21: 289–296[CrossRef][Web of Science][Medline]
Sung DY, Vierling E, Guy CL (2001) Comprehensive expression profile analysis of the Arabidopsis hsp70 gene family. Plant Physiol 126: 789–800 Turner NC, Kramer PJ (1980) Adaptation of Plants to Water and High Temperature Stress. John Wiley & Sons, New York Vierling E (1991) The roles of heat shock proteins in plants. Annu Rev Plant Physiol Plant Mol Biol 42: 579–620[CrossRef][Web of Science] Waters ER, Lee GJ, Vierling E (1996) Evolution, structure and function of the small heat shock proteins in plants. J Exp Bot 47: 325–338 Wehmeyer N, Hernandez LD, Finkelstein RR, Vierling E (1996) Synthesis of small heat-shock proteins is part of the developmental program of late seed maturation. Plant Physiol 112: 747–757[Abstract] Worley CK, Zenser N, Ramos J, Rouse D, Leyser O, Theologis A, Callis J (2000) The degradation signal of Aux/IAA proteins is important in auxin signaling. Plant J 21: 553–562[CrossRef][Web of Science][Medline]
Zhong RQ, Kays SJ, Schroeder BP, Ye ZH (2002) Mutation of a chitinase-like gene causes ectopic deposition of lignin, aberrant cell shapes, and overproduction of ethylene. Plant Cell 14: 165–179
Zolkiewski M (1999) ClpB cooperates with DnaK, DnaJ, and GrpE in suppressing protein aggregation: a novel multi-chaperone system from Escherichia coli. J Biol Chem 274: 28083–28086 This article has been cited by other articles:
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-amino-N-caproic acid, and 1.0 mM benzamidine) in a ground-glass homogenizer. Protein concentration was determined using a Coomassie Blue dye-binding assay (Ghosh et al., 1988
-crystallin domain. Cell Stress Chaperones 6: 225–237
