Mutations of genes in synthesis of the carotenoid precursors of ABA lead to pre-harvest sprouting and photo-oxidation in rice |
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Authors: | Fang Jun Chai Chenglin Qian Qian Li Chunlai Tang Jiuyou Sun Lei Huang Zejun Guo Xiaoli Sun Changhui Liu Min Zhang Yan Lu Qingtao Wang Yiqin Lu Congming Han Bin Chen Fan Cheng Zhukuan Chu Chengcai |
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Affiliation: | State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China;, Graduate University of the CAS, Beijing 100039, China;, State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China;, Centre for Biological Electron Microscopy, Institute of Biophysics, CAS, Beijing 100101, China;, State Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, CAS, Beijing 100093, China;, National Centre for Gene Research, CAS, Shanghai 200233, China;, and Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, CAS, Beijing 100101, China |
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Abstract: | Pre-harvest sprouting (PHS) or vivipary in cereals is an important agronomic trait that results in significant economic loss. A considerable number of mutations that cause PHS have been identified in several species. However, relatively few viviparous mutants in rice ( Oryza sativa L.) have been reported. To explore the mechanism of PHS in rice, we carried out an extensive genetic screening and identified 12 PHS mutants ( phs ). Based on their phenotypes, these phs mutants were classified into three groups. Here we characterize in detail one of these groups, which contains mutations in genes encoding major enzymes of the carotenoid biosynthesis pathway, including phytoene desaturase (OsPDS), ζ-carotene desaturase (OsZDS), carotenoid isomerase (OsCRTISO) and lycopene β -cyclase (β-OsLCY), which are essential for the biosynthesis of carotenoid precursors of ABA. As expected, the amount of ABA was reduced in all four phs mutants compared with that in the wild type. Chlorophyll fluorescence analysis revealed the occurrence of photoinhibition in the photosystem and decreased capacity for eliminating excess energy by thermal dissipation. The greatly increased activities of reactive oxygen species (ROS) scavenging enzymes, and reduced photosystem (PS) II core proteins CP43, CP47 and D1 in leaves of the Oscrtiso / phs3-1 mutant and OsLCY RNAi transgenic rice indicated that photo-oxidative damage occurred in PS II, consistent with the accumulation of ROS in these plants. These results suggest that the impairment of carotenoid biosynthesis causes photo-oxidation and ABA-deficiency phenotypes, of which the latter is a major factor controlling the PHS trait in rice. |
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Keywords: | rice pre-harvest sprouting photo-oxidation carotenoid biosynthesis abscisic acid |
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