Relationships between D1 protein, xanthophyll cycle and photodamage-resistant capacity in rice (Orysa sativa L.)

Relationships between D1 protein, xanthophyll cycle and subspecific differe nce of photodamage-resistant capacity have been studied in O. japonica rice varieties 02428 and 029 (photoinhibition-tolerance) and O. indica rice var ieties 3037 and Palghar (photoinhibition-sensitivity) and their reciprocal cross F-1 hybrids after photoinhibitory treatment. It was shown that PSII p hotochemical efficiency (F-v/F-m) decreased, and xanthophyll cycle from vio laxanthin (V), via anaxanthin (A), to zeaxanthin (Z) was enhanced and non-p hotochemical quenching (qN) increased accordingly in SM-pretreated leaves o f rice when the synthesis of D1 protein was inhibited, and that there was a decrease in qN and, as a result, more loss of D1 protein and a big decreas e in F-v/F-m in DTT-pretreated leaves when xanthophyll cycle was inhibited. O. japonica subspecies had a higher maintaining capacity of D1 protein and a decrease of F-v/F-m in a more narrow range, and exhibited more resistanc e against photodamage, as compared with O. indica subspecies. The above phy siological indexes in reciprocal cross Fl hybrids, though between the value s of their parents, were closer to maternal lines than to paternal lines. E xperimental results support the concept that the turnover capacity for D1 p rotein is an important physiological basis of photoinhibition-tolerance, an d will provide the physiological basis for selection of photoinhibition-tol erant parents and develop a new approach to breed hybrids with photosynthet ic efficiency.