The Status and Strategy on the Relationship Between Lipoxygenase-3 in Rice (Oryza sativa L.) Embryos and Storability

The degradation of lipids was mainly responsible for the reduction of rice quality and production of stale flavor during its storage. It was proved that LOX-3, the major component of the isozymes accounting for 80% -90% of total activity, was the key enzyme in above process. Further results indicated that the lack of LOX-3 in Daw Dam led to decrease of lipid peroxidation, alleviating the accumulation of stale flavor during storage, which is caused by hexanal, pentanal and pentanol compounds etc. Genetic survey displayed that the absence of LOX-3 was controlled by a single Mendelian recessive gene. On the other hand,three cloned LOX genes and deduced LOX genes encoding some purified LOXs could not be contributed to the embryo LOX genes by comparing biochemical characterizations of these expressed products and some purified LOXs with known LOXs in rice embryos. The future research should focus on the further influences of LOX-3-null on rice storability. Meanwhile, single-base-transversion in coding region, insertion, deletion and replacement in promoter of LOX genes were related with lipoxygenase-null genotype of soybean and pea. Therefore,the cloning of the recessive gene controlling the null of LOX-3 and its corresponding dominant gene in rice seed embryos will contribute to the understanding of the null molecular mechanism, elucidating the differences of LOX genes expression and regulation in rice embryos. In the last, the breeding strategy of new storable rice,including the theoretical and practical concepts, was surveyed.