Investigating the role of MpAL1 in drought stress responses in Malus prunifolia: insights into AL gene family functionality

Drought stress significantly impedes apple growth, development, and yield, leading to substantial economic losses within the global apple industry. Malus prunifolia (Mp), a commonly utilized apple rootstock, has shown promise in augmenting cultivated apple resistance to abiotic stress. Although Alfin-like (ALs) proteins have demonstrated pivotal roles in dicotyledonous plants' response to abiotic stresses, knowledge about AL genes in apple rootstocks is limited, and their functions remain largely elusive. In this study, we identified and characterized 10 MpAL gene members in the apple rootstock genome, confirming their localization within the nucleus. Our investigation revealed the significant regulation of MpALs' expression under drought and abscisic acid (ABA) stresses in M. prunifolia. In this study, one of the members, MpAL1, was selected for further exploration in Arabidopsis and apple to explore its potential function in response to drought and ABA stresses. The results showed that overexpression-MpAL1 transgenic apple calli grew significantly better than WT and MpAL1-RNAi lines, which regulates the accumulation of H₂O₂ and O₂^.- levels. Additionally, transgenic Arabidopsis plants overexpressing MpAL1 exhibited positively regulating anti-oxidant enzymes activities under stress treatments. Further study showed that silencing MpAL1 in apple plants showed obvious chlorosis in leaves, and accumulation of reactive oxygen species under drought stress. Moreover, our detailed analysis established that MpAL1 regulates several drought and ABA-responsive genes, exerting an influence on their expression in transgenic apple. Collectively, our findings identify MpAL1 as a positive regulator that increases drought stress in apple, shedding light on its potential significance in bolstering drought resistance in this fruit crop.