The Sorghum Research Program in Singapore

The grain sorghum (BT×623) genome has been sequenced and publicly available. We have jointly launched and finished the re-sequencing program of additional three sorghum varieties including sweet sorghum Keller. We implemented an integrative approach by using computational and experimental analyses to provide a detail insight into phenotypic, genetic variation and expression diversity between BT×623 and Keller. We have genome-widely investigated the expression divergence between BT×623 and Keller under normal and sucrose treatment. We detected more than 3000 differentially expressed genes between these two varieties. Such expression divergence was partially due to differential cis-regulatory elements or DNA methylation, which was genetically determined by functionally divergent genes between these two varieties. Our data advance the understanding of the relationship among phenotypic, genetic variation and expression diversity. On the other hand, we have also identified total of 57 sucrose metabolism related genes from 9 different gene families. Some of sucrose metabolism related genes are very conserved and only limited variation has been detected between grain and sweet sorghum. Generally, around 60-80% of genes in these nine families can be detected with variations either in single nucleotide polymorphism (SNP), insertion/deletion (Indel) or structural variation (SV). They also exhibited the difference in exon splicing and expression profiles as well as in response to sucrose treatment between grain and sweet sorghum, suggesting the divergence of sucrose metabolism pathway between these two species. These genes are currently being utilized for molecular improvement by transgenic approaches through over or down expression.