Systematic Analysis of Galactinol Synthase and Raffinose Synthase Gene Families in Potato and Their Expression Patterns in Development and Abiotic Stress Responses

Abstract

Raffinose family oligosaccharides (RFOs) are very important for plant growth, development, and abiotic stress tolerance. Galactinol synthase (GolS) and raffinose synthase (RFS) are critical enzymes involved in RFO biosynthesis. However, the whole-genome identification and stress responses of their coding genes in potato remain unexplored. In this study, four StGolS and nine StRFS genes were identified and classified into three and five subgroups, respectively. Remarkably, a total of two StGolS and four StRFS genes in potato were identified to form collinear pairs with those in both Arabidopsis and tomato, respectively. Subsequent analysis revealed that StGolS4 exhibited significantly high expression levels in transport-related tissues, PEG-6000, and ABA treatments, with remarkable upregulation under salt stress. Additionally, StRFS5 showed similar responses to StGolS4, but StRFS4 and StRFS8 gene expression increased significantly under salt treatment and decreased in PEG-6000 and ABA treatments. Overall, these results lay a foundation for further research on the functional characteristics and molecular mechanisms of these two gene families in response to ABA, salt, and drought stresses, and provide a theoretical foundation and new gene resources for the abiotic-stress-tolerant breeding of potato.

Keywords: abiotic stress; galactinol synthase; gene expression pattern; potato; raffinose synthase.

Figure 1

Distribution of the (a) StGolS and (b) StRFS genes on potato chromosomes. The scale bar on the left indicates the length (Mb) of the potato chromosome. The gray oval on the chromosome bar represents the centromere location for each chromosome.

Figure 2

Phylogenetic tree of (a) GolS and (b) RFS proteins identified in potato, tomato, and Arabidopsis. Different subfamilies of GolS and RFS proteins were highlighted by arcs with distinct colors.

Figure 3

Gene structure of StGolS genes and conserved motif analysis of StGolS proteins. (a) Gene phylogenetic tree; (b) gene structure; and (c) protein conserved motifs of StGolS proteins.

Figure 4

Gene structure of StRFS genes and conserved motif analysis of StRFS proteins. (a) Gene phylogenetic tree; (b) gene structure; and (c) protein conserved motifs of StRFS proteins.

Figure 5

Distribution of cis-acting elements in (a) StGolS and (b) StRFS gene promoters.

Figure 6

Syntenic relationships of the GolS and RFS genes among Arabidopsis, potato, and tomato. Redlines indicate the homology and evolutionary links of GolS genes, and blue lines indicate the homology and evolutionary links of RFS genes. Gray lines indicate all the syntenic blocks present in their respective genomes. The Arabidopsis chromosome was represented by the green bars, while the potato chromosome was represented by the orange bars, and the tomato chromosome was represented by the red bars.

Figure 7

Expression profiles of the StGolS and StRFS genes in different potato organs and tissues.

Figure 8

Relative expression levels of the StGolS and StRFS genes in DM test tube plantlets under salinity (NaCl), drought (PEG-6000), and ABA treatment. Gene expression is shown relative to the expression of the reference gene StActin97. Bars represent mean ± standard error (SE) of three biological replicates. Statistical significance was analyzed by the ANOVA at p < 0.05, lowercase letters indicate significant differences among different samples from each treatment and genes.