Investigation Of Salt Tolerance Of Two Maize Cultivars And Identification Of Putative Cl~- Transporters

As an important food crop,maize also serves as animal feed and biofuel.Therefore maize production has attracted heavy attention in the scope of national economy and people's livelihood.Maize is a salt sensitive plant species whose growth and yield are limited by salt stress.DMY2 and JS3 as experimental materials for this study,are long-term grown in Northern and Northwestern China,where soil salinezation is commom to observe.The physiological evaluation in the hydroponic experimental system showed that the salt tolerance and ion exclusion ability of DMY2were significantiy higher than JS3.Under moderate salt stress,the K~+/Na~+ratio in leaves of DMY2 was maintained about 10 times higher than JS3,shows a stronger ability to discharge Na~+to protect K~+.At the same time,the Cl~-content of DMY2was also significantly lower than that of JS3.The ST(salt tolerance index)values of DMY2 under salt treatment indicated that its growth remained at a state closer to that under normal conditions.This result is consistent with its strong exclusion of Na~+and Cl~-from accumulating under salt stress.In contrast,JS3 is more salt sensitive,and its biomass reduction is the largest under salt stress among the cultivars tested.The root-to-shoot ratio of JS3 remained the same when plant was treated with salt stress,indicating that the active adaptation mechanism to salt stress was insufficient in JS3.This is also consistent with its weaker salt exclusion capacity.At the molecular biology level,this study used homologous cloning to perform a preliminary functional analysis of two putatitive Cl~-transporters(GRMZM2G104542 and GRMZM2G122251)that may be involved in mediating and regulating of tissule level Cl~-transport in maize.The results showed that in the B73 background,the two genes have quite specific expression in the roots and their expression was strongly inhibited by salt stress.Bioinformatics analysis and subcellular localization experiment showed that the products of the two genes are likely to be localized on the plasma membrane.The results of heterologous expression in yeast showed that the proteins encoded by the two genes may have no transport activity for Cl~-.Further study of protein transport function,such as electrophysiological studies,is needed.