MiPP2C44 promotes early flowering in Arabidopsis and enhances abiotic stress tolerance in mango hairy roots.

Protein phosphatase 2C (PP2C) family members play important regulatory roles in plant development and abiotic stress responses, yet their functions in mango (Mangifera indica L.) remain poorly understood. In our previous research, a PP2C protein (MiPP2C44) was identified by screening a flowering-related yeast library from mango using flowering-associated proteins. In the present study, the function of MiPP2C44 was further investigated. Expression analysis revealed that MiPP2C44 was highly expressed in leaves and induced by salt and osmotic stress. Subcellular localization analysis showed that MiPP2C44 was localized in the nucleus. Overexpression of MiPP2C44 in Arabidopsis thaliana significantly promoted early flowering under long-day conditions, accompanied by upregulation of FLOWERING LOCUS T (FT) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and downregulation of FLOWERING LOCUS C (FLC). In addition, MiPP2C44 overexpression enhanced primary root growth under salt and mannitol stress and increased survival under salt and drought conditions. In transgenic mango hairy roots, MiPP2C44 overexpression significantly reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) accumulation under NaCl and PEG treatments, while increasing superoxide dismutase (SOD) activity and proline (Pro) content, indicating improved antioxidant capacity and osmotic adjustment. Yeast two-hybrid and bimolecular fluorescence complementation assays further confirmed that MiPP2C44 interacted with the TERMINAL FLOWER 1-like protein MiTFL1-1, the APETALA1-like proteins MiAP1-1 and MiAP1-2, and the bZIP transcription factors MiFD1 and MiFD2. Comparative transcriptome analysis revealed broad transcriptional changes in MiPP2C44-overexpressing mango hairy roots, including altered expression of genes related to abscisic acid (ABA) and jasmonic acid (JA) signaling, as well as selected flowering-related genes. Collectively, these results indicate that MiPP2C44 promotes early flowering in heterologous Arabidopsis, enhances abiotic stress tolerance in both Arabidopsis and mango hairy roots, and physically interacts with mango flowering-related proteins, although its role in mango flowering remains to be established.