Transcriptome Analysis of Sophora davidii Leaves in Response to Low-Phosphorus Stress

Sophora davidii is an ideal material for studying the response to low phosphorus (P) because of its strong adaptability to low-P habitats. However, to date, there has been no research on S. davidii under low-P stress. In this paper, the differentially expressed genes (DEGs) of S. davidii were studied on days 3 and 9 of low-P treatment by transcriptome sequencing and analysed with GO and KEGG analyses. Under low-P stress, the contents of antioxidants (POD, SOD and CAT), osmotic adjusters (soluble protein and proline) and anthocyanin increased. Under low-P and normal-P conditions, 323 (209 and 114 of whose expression was upregulated and downregulated, respectively) and 504 DEGs (280 and 224 of whose expression was upregulated and downregulated, respectively) were found in S. davidii on days 3 and 9, respectively. The analysis of transcriptomics data revealed certain aspects of genes regulation under low-P stress. First, several key candidate genes, such as Orphans, GNAT, bZIP, MYB, AP2-EREBP, NAC and WRKY genes, were predicted to determine tolerance to low-P stress. Second, four pathways (starch and sucrose metabolism; plant hormone signal transduction; phenylpropanoid biosynthesis; and alanine, aspartate and glutamate metabolism) were correlated with low-P stress and were highly differentially regulated in two time treatments. These results provide new insights into the complex mechanisms of the low-P response in S. davidii or even other plant species.