Isolation of three MiDi19-4 genes from mango, the ectopic expression of which confers early flowering and enhances stress tolerance in transgenic Arabidopsis

Main conclusion Three Di19-4 genes were identified in mango. Overexpression of MiDi19-4B in A. thaliana promoted earlier flowering and enhanced drought, salt, and ABA resistance. Abstract Drought-induced protein 19 (Di19) is a drought-induced protein that is mainly involved in multiple stress responses. Here, three Di19-4 genes ( MiDi19-4A/B/C ) in mango ( Mangifera indica L.) were identified, and the coding sequences (CDS) had lengths of 684, 666, and 672 bp and encoded proteins with 228, 222, and 224 amino acids, respectively. The promoters of the MiDi19-4 genes contained phytohormone-, light-, and abiotic stress-responsive elements. The MiDi19-4 genes were expressed in every tissue and highly expressed in leaves. Moreover, MiDi19-4 genes were highly correlated with the vegetative growth period and induced by polyethylene glycol (PEG) or salt stress. MiDi19-4B displayed the highest expression during the vegetative growth period and then showed decreased expression, and MiDi19-4B was highly expressed at both the late stage of the vegetative growth period and the initial stage of the flowering induction period. The 35S::GFP–MiDi19-4B fusion protein was located in the cell nucleus. The transgenic plants ectopically expressing MiDi19-4B exhibited earlier flowering and increased expression patterns of FRUITFULL ( AtFUL ), APETALA1 ( AtAP1 ), and FLOWERING LOCUS T ( AtFT ). The drought and salt tolerance of MiDi19-4B transgenic plants was significantly increased, and these plants showed decreased sensitivity to abscisic acid (ABA) and considerably increased expression levels of drought- and salt-related genes and ABA signalling pathway genes. Additionally, bimolecular fluorescence complementation (BiFC) experiments revealed that the MiDi19-4B protein interacted with CAULIFLOWER (MiCAL1), MiCAL2, MiAP1-1, and MiAP1-2. Taken together, these results highlighted the important regulatory roles of MiDi19-4B in tolerance to multiple abiotic stresses and in flowering.