Physiological And Molecular Mechanism Of Trehalose Alleviating Cadmium Toxicity In Maize Seedlings

Maize is one of important food crops in China.The stable and high yield of maize is related to the national food security.Cadmium(Cd)is a highly toxic heavy metal element in the world.Due to the discharge of industrial wastewater and waste gas and the unreasonable application of fertilizer,a large amount of Cd is released into the soil,resulting in the increasing cadmium pollution in maize producing areas,which seriously restricts the sustainable development of maize industry.The seedling stage is the most sensitive period for maize to response to environmental stress.The growth and development of the plant in the later stage and the final increase of yield benefit directly from the good foundation of the seedling stage.Therefore,it is very important to improve the cadmium resistance in maize seedlings stage.Many exogenous substances can improve the stress resistance of plants.Trehalose,as an osmotic regulator and signal molecule,plays an important role in plant stress response and defense.In this experiment,the water culture method was adopted,and the corn variety B73 was used as the material,investigate exogenous trehalose of maize seedlings under Cd stress form,dry matter accumulation,photosynthetic properties,oxidation resistance,osmotic regulation system,Cd accumulation,root cell wall components and the effect of endogenous trehalose content,and combining with the transcriptome data selection to participate in the regulation of related gene,The effect mechanism of trehalose on the growth and development of maize seedlings under Cd stress was investigated comprehensively and deeply,providing theoretical basis for the application of trehalose in maize resistance to Cd toxicity.The research conclusions are as follows:(1)Under Cd stress,exogenous trehalose treatment significantly increased the chlorophyll content and Fv/Fm in the leaves of maize seedlings,increased by 32.76% and 9.65%respectively.While increasing the content of photosynthetic pigment,it reduced the damage of Cd to the photosynthetic system,enhanced the photosynthetic capacity of plants,alleviated the toxic symptoms of Cd on the morphology of maize seedlings,and was conducive to seedling morphogenesis and dry matter accumulation.(2)Under Cd stress,exogenous trehalose could increase the activities of SOD,CAT and As A in maize seedling leaves,enhance the antioxidant capacity,reduce the content of ROS and protect the membrane system;At the same time,exogenous trehalose can increase the content of soluble protein and soluble sugar in maize leaves,reduce the content of proline,and maintain the osmotic balance of plants under Cd stress.(3)Under trehalose treatment,the content of trehalose in maize seedling leaves increased,and it can degrade excess trehalose and maintain trehalose balance by regulating trehalose enzyme activity.Exogenous trehalose could induce the increase of cellulose content in root cell wall,reduce Cd translocation factor,and reduce Cd accumulation in maize root and shoot,reducing 33.25% and 18.92% respectively.(4)The transcriptome results showed that under Cd stress,exogenous trehalose induced the up regulation of gene expression encoding oxidoreductase,heat shock protein,serine/threonine protein kinase,WRKY transcription factor,glycosyltransferase and major facilitator superfamily protein in leaves,inhibited the gene expression of HMA family members.By regulating the above genes,the ability of maize seedlings to resist Cd Stress was improved.In conclusion,under Cd stress,exogenous trehalose can reduce Cd content in roots,promote cellulose synthesis in root cell wall,inhibit gene expression of HMA family members,reduce translocation factor inhibit Cd transport to aboveground parts,reduce Cd accumulation in aboveground parts,and improve Cd avoidance ability of seedlings.At the same time,trehalose can increase the expression level of oxidoreductase gene and the activity of antioxidant enzymes under Cd stress,enhance the defense ability of ROS scavenging system and restore the oxidation imbalance caused by Cd;The increase of soluble protein and soluble sugar content also maintained the osmotic balance in vivo,protected the stability of biofilm system and improved the Cd tolerance of plants.Transcriptome analysis also found that trehalose enhanced the expression of genes related to carbohydrate metabolism,transport and defense under Cd stress,promoted the distribution and utilization of photosynthetic products,and the accumulation of stress substances initiated the defense mechanism in vivo.Therefore,exogenous trehalose improves the ability of maize seedlings to resist Cd through various ways and mechanisms,maintains the stability of chlorophyll content,reduces the damage caused by Cd to PSII complex,accumulates biomass,promotes plant growth and development,and reduces the toxic effect of Cd on plants.