THE SMALL, METHIONINE-RICH CHLOROPLAST HEAT-SHOCK-PROTEIN PROTECTS PHOTOSYSTEM-II ELECTRON-TRANSPORT DURING HEAT-STRESS

Evidence suggests that the small chloroplast heat-shock protein (Hsp) is involved in plant thermotolerance but its site of action is unknown . Functional disruption of this Hsp using anti-Hsp antibodies or addit ion of purified Hsp to chloroplasts indicated that (a) this Hsp protec ts thermolabile photosystem II and, consequently, whole-chain electron transport during heat stress; and (b) this Hsp completely accounted f or heat acclimation of electron transport in pre-heat-stressed plants. Therefore, this Hsp is a major adaptation to acute heat stress in pla nts.