A novel aquaporin geneMaSIP2-1confers tolerance to drought and cold stresses in transgenic banana

Plant aquaporins (AQPs) are subdivided into eight groups: PIPs, NIPs, GIPs, HIPs, XIPs, LIPs, TIPs, and SIPs. However, the genetic function and physiological mechanisms of the SIP group in abiotic stress response in plants remains unknown. In this study, we cloned and characterized a banana SIP groupAQPgene, designatedMaSIP2-1.MaSIP2-1showed upregulation after osmotic, salt, and cold treatments. Overexpression ofMaSIP2-1in bananas resulted in smaller leaf area and lower plant height than wild-type (WT) plants under normal growth conditions. Lines over-expressingMaSIP2-1showed increased tolerance to drought and cold stresses, demonstrating that transgenic lines had higher content of chlorophyll, proline, soluble sugar, and abscisic acid (ABA), but lower levels of ion leakage (IL), malondialdehyde (MDA), H2O2, and gibberellins (GAs), than WT after drought, cold, and recovery conditions. Moreover, transgenic lines had higher expression of ABA biosynthetic and responsive genes than WT under drought and cold conditions. Taken together, our results show thatMaSIP2-1plays a positive role in dwarfing and tolerance to drought and cold stresses through improved osmotic adjustment, less membrane injury, and changes in ABA and GA levels. Therefore,MaSIP2-1has the potential for utilization to improve abiotic stress tolerance in crop breeding.