This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (23) Citing Articles via Google Scholar Google Scholar Articles by Arruda, P. Articles by Rognes, S. E. Search for Related Content PubMed PubMed Citation Articles by Arruda, P. Articles by Rognes, S. E. Agricola Articles by Arruda, P. Articles by Rognes, S. E.

Articles

Regulation of Aspartate Kinase Isoenzymes in Barley Mutants Resistant to Lysine plus Threonine ¹

Construction and Analysis of Combinations of the Lt1a, Lt1b, and Lt2 Mutant Genes

Biochemistry Department, Rothamsted Experimental Station, Harpenden, Hertfordshire AL5 2JQ, United Kingdom

Two homozygous mutant lines of barley (Hordeum vulgare L.) R3202 (Lt1b/Lt1b) and R3004 (Lt2/Lt2), are resistant to lysine plus threonine. They contain aspartate kinase isoenzymes with lost or decreased feedback sensitivity to lysine in either isoenzyme AKII (R3202) or isoenzyme AKIII (R3004). A homozygous double mutant line (Lt1b/Lt1b, Lt2/Lt2) has now been constructed that grows vigorously on 8 millimolar lysine, 8 millimolar threonine, and 1 millimolar arginine. Both AKII and AKIII from the double mutant have altered lysine sensitivities, identical to those previously observed in R3202 and R3004, respectively. Aspartate kinase activity in extracts of leaves, roots, and the maturing endosperm of the double mutant was much less sensitive to lysine inhibition than the enzyme in comparable extracts of the parent cv Bomi, suggesting that aspartate kinase is expressed in a similar manner in different tissues of barley.

A further mutant, R2501, resistant to lysine plus threonine has now given rise to a homozygous line (Lt1a/Lt1a), which had previously not been possible. AKII isolated from the homozygous line was completely insensitive to 10 millimolar lysine; however, the combined action of 10 millimolar lysine and 0.8 millimolar S-adenosylmethionine inhibited it by 60%, demonstrating the retention of some of the regulatory characteristics of the wild type enzyme.

³ Present address: Department of Botany, P.O. Box 1045, University of Oslo, Blindern, Oslo 3, Norway.

¹ Part of this was supported by Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (P. A.) and NATO research Grant RG 255.80 (S. W. J. B. and S. E. R.).

This article has been cited by other articles:

				L. M. Voll, E. E. Allaire, G. Fiene, and A. P.M. Weber The Arabidopsis phenylalanine insensitive growth Mutant Exhibits a Deregulated Amino Acid Metabolism Plant Physiology, October 1, 2004; 136(2): 3058 - 3069. [Abstract] [Full Text] [PDF]