Analysis of the SPX gene family in <i>Vitis vinifera</i> and <i>Vitis amurensis</i> and its expression under phosphorus stress

Only a small amount of phosphorus is absorbed and utilized in the soil. The SPX (SYG1, PHO81, XPR1 acronyms) gene family is important in controlling phosphorus uptake, transport, and utilization on a molecular level. However, their systematic identification in grapes is still unclear. The Vitis vinifera and Vitis amurensis databases revealed a total of 37 SPX genes, with 16 VvSPX genes and 21 VaSPX genes placed on 10 chromosomes each. VvSPX and VaSPX genes are grouped into four subfamilies and contain phosphorus stress response elements such as P1BS and MBS. The highest number of genes were widely distributed in the plasma membrane, followed by the nucleus and cytoplasm. Chip data analysis showed that VvSPX16 had the highest expression level in leaves. Collinearity among intraspecifics revealed that Vitis vinifera and Vitis amurensis had a stronger collinearity relationship with Arabidopsis thaliana than Oryza sativa. Real-time quantitative PCR revealed that roots were more sensitive to low Pi than leaves under Pi stress conditions. VvSPX2, VvSPX4, VvSPX11, VaSPX11, VaSPX12, VaSPX13, and VaSPX20 showed a particularly strong response to excess Pi. VvSPX2, VvSPX4, VvSPX11, VaSPX3, VaSPX11, VaSPX13, and VaSPX21 were most highly expressed in roots at 24 h of low phosphorus stress. Phosphate deprivation dramatically increased the expression of VvSPX9, VvSPX11, VaSPX10, and VaSPX21 in both roots and leaves, suggesting that these genes might be important candidate genes for phosphate famine in grapes. This provided a reference for further research on their mechanisms of action in phosphorus stress response.