Changes in temperature and light, for example, are most effective at the milky stage of grain filling. Meanwhile, conditions of water www.selleckchem.com/products/brefeldin-a.html and nutrient in the field also play important roles on grain chalkiness. Despite its economic importance, only few genes have been functionally identified to be associated with endo sperm chalkiness. This analysis, together with a previous transcriptome analysis on chalkiness formation under higher temperature, has identified a set of differen tially expressed genes that may contribute to endosperm chalkiness. The identified candidate genes may serve as excellent starting materials for dissecting the pathway controlling rice endosperm development at the molecular level.

Notably, most of these genes identified in this study belong to six major categories including cell res cue defense, free radical clearance and redox homeosta sis, signal transduction, hormone response, protein biosynthesis and degradation, and carbohydrate metabo lism. Our data also showed that, similar to the effect of high temperature, expression of numerous genes was affected under this genetic background, but surprisingly, quite a few of these genes were oppositely regulated in CSSL50 1 when compared with the effect under the high temperature conditions. Thus, the use of a geneti cally stabilized line for endosperm chalkiness study is complementary to the previous physical stress based studies and should provide novel information regarding the molecular mechanism for chalky endosperm forma tion in rice.

Enhanced starch synthesis causes imbalanced starch composition in CSSL50 1 Previously, chalky grains were found to have lower starch content. For CSSL50 1, its grains contain higher percentage of sucrose, amylose, starch, and even protein content when compared with the normal rice cultivar Asominori. Enzymes, such as SuSy, AGPase, SBE and DBE, exhibit higher activities at 15 DAF in CSSL50 1, correlating with the higher expression levels of corresponding genes that were detected in our micro array data. Since the shape and the arrangement of starch granule are closely related to endosperm chalki ness in rice, it is reasonable to conclude that a coordinated and balanced action of starch synthetic enzymes are critical to the prevention of chalky endo sperm formation. Endosperm development is a process of proper starch composition and accumulation.

Gradual and smooth grain filling pace is required to form normal, translucent grains as seen in Asominori. CSSL50 1 has a higher grain filling rate which may give insufficient time for long chain amylopectin to be synthesized, resulting in a relative higher percentage of Entinostat short chain amylopec tin when compared with Asominori. Consis tent with our results, the decrease of 10 14 DP amylopectin was also observed when rice grains ripened under high temperatures.