EXPRESSION LEVEL OF Sh2 AND Bt2 GENES IN SOME ADVANCED CORN LINES UNDER TROPICAL ENVIRONMENT

Abstract

The rate-limiting step in starch synthesis entails the synthesis of ADP-Glc from Glc-1-P and ATP by AGPase. AGPase is a heterotetramer composed of two large subunits encoded by Sh2 and two small subunits encoded by Bt2. We examined the transcript level of each gene that encodes AGPase through quantitative real-time PCR (qRT_PCR) within endosperm and leaf tissues from 6 newer composite corn lines. The Sh2 and Bt2 genes presented upregulated expression levels in leaf and endosperm tissue. The highest expression level of these two genes in leaf tissues was observed in UM 1 with 6.96 fold and in UM 11 with 3.94 fold respectively. Meanwhile, the highest transcript level of Sh2 and Bt2 genes in endosperm tissues were observed in UM 2 with 5.96 fold and UM 1 with 7.36 fold respectively. The correlation coefficient between the expression levels of the Sh2 gene and the morphological traits in endosperm tissue indicated that it was significantly and positively correlated with ear length (0.75), ear weight (0.74) and yield (0.66). Meanwhile , the correlation coefficient results indicate that the expression level of Bt2 in endosperm tissue was significantly and positively correlated with1000 kernel weight (0.93), yield (0.90), ear weight (0.87) and ear length (0.87). In conclusion, via cross transformation approaches, two main yield-related genes (Sh2 and Bt2) were modified in the new advanced corn lines. Overexpression of Sh2 and Bt2 genes can increase the starch content through enhancing the activity of AGPase and subsequently the yield enhancement occurred.