Abstract:

Objective ​​Light-harvesting complexes (LHCs)​​ serve as essential structural components of the photosynthetic apparatus and are also implicated in the responses to abiotic stress. In this study, bioinformatics analysis was carried out to identify the LHC gene family in foxtail millet (Setaria italica) at the whole-genome level, with further analysis of its expression profiles under diverse abiotic stress conditions. It would be helpful for the functional study of genes related to photosynthesis and provide theoretical support for molecular breeding in foxtail millet. Method The members of LHC gene family were obtained from the foxtail millet genome. Subsequently, a series of analysis were conducted, including phylogenetic analysis, physicochemical properties and subcellular localization, gene structure, conserved motif identification, and promoter cis-acting elements. Transcriptomic data and RT-qPCR were combined to investigate gene expression across different tissues and under abiotic stress conditions. Result A total of 30 LHC gene family members were identified and classified into four subfamilies of Lhc, Lil, PsbS and FCⅡ. These genes were unevenly distributed on nine chromosomes. Synteny analysis revealed one pair of segmental duplications and two pairs of tandemly duplicated genes. Cis-acting elements in the gene promoters of all members included light-responsive, hormone-responsive, abiotic stress-responsive and plant defense/stress-responsive elements. Protein structure prediction indicated that secondary structures were predominantly α-helices and random coils, while tertiary structures demonstrated subfamily-specific features. Strong protein-protein interactions were observed within the SiLhc subfamily. Expression analysis showed that 27 SiLHCs were highly expressed in the leaves. Members within the same subfamily presented functional divergence in response to identical stress conditions, while genetic background further drove differential abiotic stress responses. SiLhcb4, SiLhcb5 and SiFCⅡ were identified as abiotic stress-sensitive genes by RT-qPCR analysis, displaying significant downregulation under drought, salinity, and alkaline stress conditions. Conclusion The structural and functional similarities among the four subfamily members of SiLHC, combined with their divergent transcriptional responses to abiotic stresses, suggested their roles in the photosynthetic system and the regulation of responses to abiotic stress.

Key words: Setaria italica, LHC gene family, abiotic stress, photosynthesis, gene expression, drought stress, salt stress, alkali stress