Genome-Wide Identification and Characterization of SPX Domain-Containing Members and Their Responses to Phosphate Deficiency in .

The importance of SPX domain-encoding proteins to phosphate (Pi) homeostasis and signaling pathways has been well-documented in rice and . However, global information and responses of SPX members to P stress in allotetraploid , one of the world's major oil crops that is sensitive to P deficiency, remain undefined. We identified a total of 69 SPX domain-containing genes in the genome. Based on the domain organizations, these genes were classified into four distinct subfamilies-SPX (11), SPX-EXS (43), SPX-MFS (8), and SPX-RING (7)-that represented clear orthologous relationships to their family members in . A -element analysis indicated that 2 ∼ 4 P1BS elements were enriched in the promoter of SPX subfamily genes except . RNA-Seq analysis showed that genes were differentially expressed in response to Pi deficiency. Furthermore, quantitative real-time reverse transcription PCR revealed that nine SPX subfamily genes were significantly induced by Pi starvation and recovered rapidly after Pi refeeding. A functional analysis of two paralogous genes in transgenic indicated their functional divergence during long-term evolution. This comprehensive study on the abundance, molecular characterization and responses to Pi deficiency of genes provides insights into the structural and functional diversities of these family members in and provides a solid foundation for future functional studies of genes. The genome-wide identification and characterization of SPX genes in and their responses to Pi deficiency provide comprehensive insights into the structural and functional diversities of the family members in and their potential in Pi homeostasis and signaling responsiveness to Pi stress.