Overexpression of ZmSUS1 gene alters the content and composition of endosperm starch in maize (Zea mays L.)

Cereal crops accumulate starch in seeds as an energy reserve. Sucrose synthase (SuSy) plays an important role in grain starch synthesis. In this study, ZmSUS1 was transformed into maize inbred line KN5585, and transgenic plants were obtained. Compared with the control, the content and activity of SuSy were significantly increased, the amylose content in mature seeds of transgenic maize increased by 41.1-69.2%, the total starch content increased by 5.0-13.5%, The 100-grain weight increased by 19.0-26.2% and the average diameter of starch granules increased by 10.8-17.2%. These results indicated that overexpression of ZmSUS1 can significantly improve the traits of maize kernels and obtain new lines with high amylose content. It was also found that ZmSUS1 may increase the amylose content by regulating the expression of Shrunken2 (Sh2) and Brittle2 (Bt2) which encodes endosperm ADP-glucose pyrophosphorylase (AGPase) size subunits, and the expression of Granule bound starchsynthase1 (GBSS1) and Starch synthase1 (SS1) which encodes starch synthase. This study proved the important role of ZmSUS1 in maize starch synthesis, and provided a new technology strategy for improving corn starch content and yield. Overall design: In this study, ZmSUS1 (Zm00001d047253) was transformed into a maize inbred line to study the effect of its overexpression on the structure and content of maize starch and the expression of genes related to starch synthesis. A transgenic strain (T) was selected with its non-transgenic negative control (CK) for RNA-seq analysis, with three biological replicates selected each. RNA is extracted from corn kernels after 10 days of pollination.