Grain Quality and Starch Physicochemical Properties of Chalky Rice Mutant

Rice mutants with altered starch components and properties are important genetic resources for grain quality and starch structure analysis. Accordingly, in the present study, two mutants of the transcription factor OsbZIP09 were generated (osbzip09a and osbzip09b), and the rice grain quality and physicochemical starch properties of the mutant and wild-type lines were compared. The OsbZIP09 mutants exhibit a chalky grain owing to loosely packed, small, spherical starch granules in the ventral region of the endosperm. Furthermore, grain-quality profile analysis showed that OsbZIP09 deficiency leads to increased apparent amylose content but decreased gel consistency. Structural analysis of the mutant starches revealed that the mutant rice lines contain more amylopectin short chains and fewer intermediate chains, leading to lower crystallinity and lower gelatinization properties than those of the wild-type rice. Moreover, the OsbZIP09 mutants rice presented a significantly higher pasting curve and corresponding parameters than the wild-type rice. The results from this work strongly indicate that the transcription factor OsbZIP09 plays an important role in rice grain quality and starch fine structure modification, and extend our understanding of starch biosynthesis in rice endosperm.