[Identification, expression profiling, and natural allelic variation analysis of the Sbsgr gene family in sorghum]

Stay-green (sgr) genes encode magnesium dechelatases, which catalyze chlorophyll degradation and play a pivotal role in regulating plant senescence and determining crop yields. This study systematically investigated the biological functions of Sbsgr genes in sorghum and their roles in stress responses, aiming to provide a reference for further research on the molecular mechanisms of sgr genes. Through integrated bioinformatics and molecular biological approaches, we systematically characterized the Sbsgr gene family in sorghum in terms of gene structures, protein physicochemical properties, promoter cis-acting elements, expression profiles, interacting proteins, and natural allelic variations. The results indicated that sorghum carried two sgr homologous genes. Sbsgr1 was an sgr homolog, while Sbsgr2 was an sgr-like homolog. The promoter region of Sbsgr harbored cis-acting elements associated with drought stress and abscisic acid responses. The expression patterns of the two genes differed significantly. Sbsgr1 was primarily expressed in leaves, panicles, and seeds, whereas Sbsgr2 showed high expression levels in leaves. Under drought, low nitrogen, and infection by Sporisorium reilianum, the expression of Sbsgr1 was significantly upregulated, while that of Sbsgr2 was suppressed. Three varieties with strong stay-green traits were preliminarily identified, and two SNP sites in Sbsgr1 were detected in stay-green lines such as 'B35'. The results of this study can provide a reference for further in-depth research on the molecular mechanism of the sgr gene.