Genome-wide analysis of the mango SPL family and overexpression of MiSPL13 confers early flowering and stress tolerance in transgenic Arabidopsis

SQUAMOSA promoter binding protein-like (SPL) genes played important roles during plant growth and development. However, there have been no studies on SPL genes in mango (Mangifera indica L.). In the present study, a total of 26 SPL family members were first identified and analysed in the `SiJiMi' mango genome, and these genes were classified into nine subfamilies (G1 - G9) according to conserved gene structures and protein motifs. Expression analysis revealed that the MiSPL genes were expressed in all the tested organs, albeit with expression level differences. Fifteen of them exhibited the highest expression in flowers at the initial flowering stage. Furthermore, most of the MiSPLs were expressed in response to exogenous gibberellin (GA(3)) and prohexadione-calcium (Pro-Ca) treatments. MiSPL13 was primarily expressed in flowers and significantly upregulated in buds under GA(3) and Pro-Ca treatments on the 2nd and 6th days, respectively. The full length cDNA sequence of MiSPL13 was 1116 bp, encoding 372 amino acids. MiSPL13 was located in the nucleus and had transcriptional activation activity in yeast. Overexpression of MiSPL13 not only promoted early flowering in transgenic Arabidopsis, which increased the expression levels of AtAP1, AtSOC1, and AtFUL, but also significantly increased tolerance to drought, abscisic acid (ABA) and GA(3) while showing sensitivity to Pro-Ca treatment.