High-quality genome of guar (Cyamopsis tetragonoloba) provides the new insights into the biosynthesis and origination of galactomannans in Fabaceae family

Guar (Cyamopsis tetragonoloba) is a Fabaceous crop widely cultivated in tropical and subtropical regions. Guar gum, a galactomannan polysaccharide extracted from its seeds, is extensively utilized across food, pharmaceutical, cosmetic, and petroleum industries, underscoring its considerable economic importance. In this study, we present a 516 Mb chromosome-level genome assembly of guar and explore its evolutionary history within the Fabaceae family. Genome synteny and synonymous nucleotide substitution rates (Ks) analyses indicate that guar, along with other Faboideae species, shared one whole-genome duplication (WGD) events, occurring ~58 million years ago (MYA). Transcriptome profiling revealed that key genes of ManS and GMGT1 involved in galactomannan biosynthesis are highly expressed in the endosperm, while other Fabaceae species that do not synthesize galactomannan show significantly lower expression of these genes, suggesting that transcriptional regulation of ManS and GMGT1 play a central role in galactomannan production. This study offers a high-quality genomic resource for guar, clarifies its phylogenetic placement within the Fabaceae, and provides novel molecular insights into the biosynthesis and evolutionary origin of galactomannan.