Functional identification of mango MiEXPLA1a2 and MiEXPA4e1 genes in transgenic Arabidopsis and tomato

Expansin (EXP) is an intrinsic regulator of plant cell expansion, and have been shown to play a role in each stages of plant growth and development. But has not yet been fully studied in mango. In this experiment, two pairs of homologous genes MiEXPA1s and MiEXPA4s were firstly excavated from mango genome. qRT-PCR analysis showed that the expression of MiEXPA1a2 was gradually increased with the development of mango fruits, while MiEXPA4e1 has the opposite expression pattern. In this study, the functions of two genes were explored by overexpression in Arabidopsis and tomato. MiEXPLA1a2 and MiEXPA4e1 genes with opposite expression levels showed similar gene functions. Compared with wild-type Arabidopsis (WT), overexpression of MiEXPA1a2 and MiEXPA4e1 Arabidopsis promoted early flowering, increased rosette leaves number, caused dwarf plants, and reduced the number of seeds. In addition, MiEXPA1a2 and MiEXPA4e1 transgenic plants significantly increased root length and survival rate under drought and salt stress treatments. It was also found that MiEXPA1a2 and MiEXPA4e1 promoted root length in response to gibberellin treatment, while ABA significantly inhibited it. We found similar phenotypes to Arabidopsis in transgenic tomato plants, such as promoted early flowering, reduced plant height, increased sepal length, affected the fruit and seed quality. Interestingly, MiEXPA4e1 is significantly shorter the pod length in Arabidopsis and reduced the fruit weight in tomato, while MiEXPA1a2 does not have this phenomenon. In conclusion, MiEXPLA1a2 and MiEXPA4e1 genes have potential applications in regulating plant flowering, regulating phenotype, and improving stress response.