Abstract
The pyrroline-5-carboxylate synthetase (P5CS), succinic semialdehyde dehydrogenase (SSADH) and dehydrin (DHN) genes play major roles in the response to drought stress. This is the first study to identify the P5CS, SSADH and DHN genes in Solanum lycopersicum viagenome-wide analysis under drought stress. The qRT‒PCR results indicated that P5CSand DHN were upregulated, with fold changes of 2.39 and 1.23, respectively, whereas the expression level of SSADH decreased to 0.73. Genome-wide analysis revealed 2 P5CS, 16 SSADH and 2 DHN genes in S. lycopersicum. P5CS genes were found on chromosomes 6 and 8. The SSADH genes were found on chromosomes 1, 2, 3, 5, 6, 7, 8, 9 and 12. DHN genes were found on chromosomes 2 and 4. The Ka/Ks ratios indicated that the P5CS, SSADH and DHN genes were influenced primarily by purifying selection, which indicated that the P5CS, SSADH and DHN genes received strong environmental pressure during evolution. The number of duplications of the P5CS paralogous gene pairs ranged from approximately 40.030 Mya. The duplication time of the SSADH paralogous gene pair ranged from approximately 7.892 to 210.890 Mya. The number of duplications of the DHNparalogous gene pairs ranged from approximately 189.799 Mya. Synteny analysis of the P5CS, SSADH and DHN genes revealedcollinearity orthologous relationships in S. tuberosum and A. thaliana but no orthologs of the P5CS, SSADH and DHN genes with O. sativa. In addition, collinearity analysis revealed that 2 orthologous P5CS genes, 18 orthologous SSADH genes and 2 orthologous DHN genes were paired with those in S. tuberosum. Collinearity analysis revealed that 14 orthologous SSADH genes and 1 orthologous DHN gene were paired with those in A. thaliana. Our present study increases our knowledge about the characteristics and roles of the P5CS, SSADH and DHN genes in drought stress in S. lycopersicum.