PT  - JOURNAL ARTICLE
AU  - Allen, Lisa J.
AU  - MacGregor, Kennaway B.
AU  - Koop, Randall S.
AU  - Bruce, Doug H.
AU  - Karner, Julie
AU  - Bown, Alan W.
TI  - The Relationship between Photosynthesis and a Mastoparan-Induced Hypersensitive Response in Isolated Mesophyll Cells
AID  - 10.1104/pp.119.4.1233
DP  - 1999 Apr 01
TA  - Plant Physiology
PG  - 1233--1242
VI  - 119
IP  - 4
4099  - http://www.plantphysiol.org/content/119/4/1233.short
4100  - http://www.plantphysiol.org/content/119/4/1233.full
SO  - Plant Physiol.1999 Apr 01; 119
AB  - The G-protein activator mastoparan (MP) was found to elicit the hypersensitive response (HR) in isolatedAsparagus sprengeri mesophyll cells at micromolar concentrations. The HR was characterized by cell death, extracellular alkalinization, and an oxidative burst, indicated by the reduction of molecular O2 to O2 ⋅ −. To our knowledge, this study was the first to monitor photosynthesis during the HR. MP had rapid and dramatic effects on photosynthetic electron transport and excitation energy transfer as determined by variable chlorophyll a fluorescence measurements. A large increase in nonphotochemical quenching of chlorophylla fluorescence accompanied the initial stages of the oxidative burst. The minimal level of fluorescence was also quenched, which suggests the origin of this nonphotochemical quenching to be a decrease in the antenna size of photosystem II. In contrast, photochemical quenching of fluorescence decreased dramatically during the latter stages of the oxidative burst, indicating a somewhat slower inhibition of photosystem II electron transport. The net consumption of O2 and the initial rate of O2 uptake, elicited by MP, were higher in the light than in the dark. These data indicate that light enhances the oxidative burst and suggest a complex relationship between photosynthesis and the HR. Fmmaximal fluorescenceFm′maximal fluorescence in any light-adapted stateFominimal (background) fluorescenceFo′minimal fluorescence in any light-adapted stateFssteady-state fluorescenceHRhypersensitive responseMPmastoparanPAMpulse-amplitude-modulatedQAthe primary quinone electron acceptor of PSIIqNnonphotochemical quenchingqPphotochemical quenching