Genome-wide identification of family genes in C, C-C, and C Salsoleae s.l. species.

C photosynthesis is a carbon-concentrating mechanism that evolved to enhance photosynthetic efficiency under conditions favoring photorespiration, such as high temperature, low atmospheric CO, and aridity. Photorespiration is considered the primary driving force on the evolution of C photosynthesis. Serine hydroxymethyltransferase (SHMT) plays a crucial role in one-carbon metabolism and photorespiration. However, there is a lack of comprehensive bioinformatics investigation on the gene family across different photosynthetic types, specifically comparing C, C, and C-C intermediate species. In this study, we conducted a systematic analysis of the gene family regarding gene structure, phylogenetic relationships, expression patterns, and cis-acting element in four Salsoleae species, including C species , C-C intermediate species , and two C species and . The results indicated that 4-5 members were identified in these four species. No fragment duplication were identified, which may explain the lower number of members in each Salsoleae species. The range of exon numbers varied from 4 to 15. Phylogenetic analysis showed that the from Salsoleae species can be classified into four distinct classes, with most members displaying conserved gene structure and motif numbers, except for and , which had divergent gene structures. The in Salsoleae species did not exhibit organ-specific expression patterns; however, variations in expression were observed among the different members. Analysis of newly sequenced Salsoleae transcriptomes data and published data from five other genera (, , , , and ) revealed that, compared to C and C-C intermediate species, only mitochondrial-localized, leaf preferential showed a low expression among members, probably evolved in C photosynthesis evolution. The MYB transcription factors were predicted to be the most significant regulators of in three Salsoleae species and the second most significant in . These results may provide valuable information for further analyses, particularly in the evolutionary study of Salsoleae .