Characterization of Early Nodulin 93 (ENOD93) on the mucilage secretion of aerial roots in sorghum

Sorghum ( Sorghum bicolor ) serves dual roles as a staple food crop providing energy and nutrition for human’s consumption, and as an economic crop utilized in the production of saccharides, silage, and bioethanol. The biological significance of aerial root mucilage secretion lies in biological nitrogen fixation, through which sorghum acquires approximately 40% of its nitrogen from the atmosphere. Prior transcriptomic data indicated tissue-specific overexpression of ENOD93 in aerial roots. This study presents the characterization of the ENOD93 multigene family in sorghum. Sobic.004G099900 exhibited distinct evolutionary patterns compared to the other six members in chromosomal localization, gene structure, physicochemical properties, domain architecture, subcellular targeting, and phylogenetic reconstruction, suggesting its emergence earlier in evolutionary history. Expression profiling across tissues and stress conditions revealed significant nitrogen responsiveness. Mucilage secretion capacity was positively correlated with the ENOD93 expression level at the developmental stage and immersion in vitro. Collectively, these findings indicate functional divergence within the ENOD93 multigene family during evolution. The ENOD93 expression potentially respond to nitrogen fluctuations in the mucilage microenvironment, suggesting that the candidate positive genes of aerial root mucilage secretion. This work advances understanding of ENOD93 evolutionary patterns in sorghum and provides some clues for the exploration of genes regulating mucilage secretion in aerial roots.