Aquaporin ZmPIP2;4 promotes tolerance to drought during arbuscular mycorrhizal fungi symbiosis

Aquaporins and arbuscular mycorrhizal fungi (AMF) have been recognized to enhance plant tolerance to drought stress. However, the involvement of aquaporins in AMF-modulated mechanisms and the role of AMF-induced aquaporin genes in maize under drought stress remains unclear. The present study investigated the symbiotic relationship between maize and AMF in response to drought. Our aim was to elucidate the impact of AM-inducible aquaporin ZmPIP2;4 on mycorrhiza formation and drought tolerance.

The container experiment of the zmpip2;4 mutant verified the function of ZmPIP2;4 upon drought during AMF symbiosis and the Lotus japonicus (L. japonicus) overexpressing ZmPIP2;4 (ZmPIP2;4-OE) was also used to further investigate the drought-resistant function of ZmPIP2;4.

ZmPIP2;4 was significantly induced upon drought treatment during AMF symbiosis. The biomass, colonization rate, relative water content (RWC), photosynthesis, POD and SOD activities, proline content, and the expression of other drought-related genes P5CS4, NECD1, and LEA3 were lower in the zmpip2;4 mutant than that in the wild-type after inoculation with the AMF under drought stress, indicating that ZmPIP2;4 promoted drought tolerance of maize during AMF symbiosis. The proline content, POD and SOD activities of ZmPIP2;4-OE L. japonicus plants were higher than those of wild-type MG20, suggesting that ZmPIP2;4 enhanced the drought tolerance of L. japonicus plants.

AMF symbiosis induced the expression of ZmPIP2;4 gene in the maize roots, and in return, ZmPIP2;4 further facilitated the AM symbiosis in roots. The results indicated that ZmPIP2;4 was influential in promoting maize’s tolerance to drought stress during AMF symbiosis.