Comparative transcriptome and metabolome profiling in the maturing seeds of contrasting cluster bean (Cyamopsis tetragonoloba L. Taub) cultivars identified key molecular variations leading to increased gum accumulation.

Abstract

Cluster bean (Guar) is the major source of industrial gum. Knowledge on the molecular events regulating galactomannan gum accumulation in guar will pave way for accelerated development of gummy guar genotypes. RNA Seq analysis in the immature seeds of contrasting cluster bean genotypes HGS 563 (gum type) and Pusa Navbahar (vegetable type) resulted in the generation of 19,855,490 and 21,488,472 quality reads. Data analysis identified 4938 differentially expressed genes between the gummy vs vegetable genotypes. A set of 2241 genes were up-regulated and 2587 genes were down-regulated in gummy guar. Significant up-regulation of genes involved in the biosynthesis of galactomannan and cell wall storage polysaccharides was observed in the gummy HGS 563. Genes involved in carotenoids, flavonoids, non mevalonic acid, terpenoids, and wax metabolism were also up-regulated in HGS 563. Mannose and galactose were the major nucleotide sugars in Pusa Navbahar and HGS 563 immature seeds. Immature seeds of HGS 563 showed high concentration of mannose and galactose accumulation compared to Pusa Navbahar. qRT-PCR analysis of selected genes confirmed the findings of transcriptome data.