Overexpression of a Novel Gene from the Banana () Confers Increased Salt Stress Tolerance.

Rho-like GTPases from plants (ROPs) are plant-specific molecular switches that are crucial for plant survival when subjected to abiotic stress. We identified and characterized 17 novel ROP proteins from (MaROPs) using genomic techniques. The identified MaROPs fell into three of the four previously described ROP groups (Groups II⁻IV), with MaROPs in each group having similar genetic structures and conserved motifs. Our transcriptomic analysis showed that the two banana genotypes tested, Fen Jiao and BaXi Jiao, had similar responses to abiotic stress: Six genes (, , , , , and ) were highly expressed in response to cold, salt, and drought stress conditions in both genotypes. Of these, was most highly expressed in response to salt stress. Co-localization experiments showed that the MaROP5g protein was localized at the plasma membrane. When subjected to salt stress, transgenic overexpressing had longer primary roots and increased survival rates compared to wild-type . The increased salt tolerance conferred by might be related to reduced membrane injury and the increased cytosolic K⁺/Na⁺ ratio and Ca concentration in the transgenic plants as compared to wild-type. The increased expression of salt overly sensitive (SOS)-pathway genes and calcium-signaling pathway genes in -overexpressing reflected the enhanced tolerance to salt stress by the transgenic lines in comparison to wild-type. Collectively, our results suggested that abiotic stress tolerance in banana plants might be regulated by multiple , and that might enhance salt tolerance by increasing root length, improving membrane injury and ion distribution.