Response of Atalantia buxifolia to Salt Stress Based on Physiological and Transcriptome Analysis

As a coastal brush, Atalantia buxifolia is a good rootstock of citrus plants around sea shores, but its salt tolerance has not been studied. In order to explore the salt tolerance of A. buxifolia, its seeds and seedlings were subjected to NaCl stress treatment, followed by phenotypic observation and biochemical and transcriptome analysis. Results showed that the increase in NaCl concentrations resulted in the decrease in germination rates, germination potential, germination index, and vigor index of A. buxifolia seeds, as well as growth of epicotyl and radicle, and biomass of A. buxifolia seedlings. However, the seeds of A. buxifolia could adapt to the growth of 100 mM NaCl concentration to a certain extent. The levels of malondialdehyde (MDA) and relative electrolyte leakage increased with the increase in NaCl concentrations. However, under treatment of 100 mM NaCl, the biomass, POD, CAT, APX, GSH, AsA, H₂O₂, MDA, and relative electrolyte leakage of A. buxifolia seedlings did not show significant changes compared with the control treatment. Transcriptome analysis showed that expression of differential genes increased with the increase in NaCl concentrations. GO enrichment showed that the most annotated genes were metabolic process, cell and cell composition, and binding. The KEGG pathway annotation shows that differential genes were mainly enriched in some pathways, such as photosynthesis antenna proteins, plant hormone signal transduction, glutathione metabolism, and starch and sucrose metabolism. In addition, differentially expressed genes had been annotated into 45 transcription factor families, including the largest number of bHLH, NAC, WRKY, MYB, and bZIP families. The results provide a basis for further understanding the salt tolerance mechanism and exploring related salt tolerance genes of A. buxifolia.