Mechanisms Of LHCB7 Regulating Tomato Responding To Glyphosate Hormesis

Glyphosate is the most widely used herbicide in the world,and it has been proved with hormesis effects on plant growth and photosynthesis,that is,low-dose promotion while high-dose inhibition.Photosystem II is involved in regulating plant response to glyphosate toxic excitatory effect,but its intrinsic mechanism has not been elucidated.The research group previously used CRISPR/Cas9 gene editing system to construct and obtain tomato LHCB7（encoding chlorophyll a/b binding protein 7）homozygous mutant.On this basis,this research further explores the dose-response relationship of glyphosate hormesis effect,and analyzes the molecular mechanism of LHCB7 regulating plant response to glyphosate hormesis.We obtained main results as follows:（1）Determine the dose-response relationship of glyphosate-induced hormesis effect on tomato plants and construct a hormesis model.The concentration range of glyphosate-induced hormesis effect on tomato plants is 0.005-13 mg L^-1,which can produce a maximum of 162%increase in plant height.Transcriptome sequencing analysis reveals that photosystem II is involved in regulating plant response to glyphosate hormesis.（2）LHCB7 is involved in regulating plant response to glyphosate hormesis.The dose-effect relationship of glyphosate hormesis effect on LHCB7 genome-editing mutants is different from that on wild-type plants,which is related to the phenotype alterations including photosynthetic pigment content,reactive oxygen species ROS level,chlorophyll spontaneous fluorescence.（3）Glyphosate hormesis can enhance plant tolerance to photosynthesis inhibitor diuron.Glyphosate hormesis changes thylakoid membrane components,increases photosynthetic efficiency,enhances tolerance to photosynthesis inhibitor diuron,and the wild-type plants show more significant tolerance increase than the mutants,indicating that LHCB7 directly participates in regulating hormesis.（4）Non-photochemical quenching（NPQ）is involved in regulating plant response to glyphosate hormesis effect.Glyphosate hormesis increases NPQ efficiency and promotes photoprotection;low dose of glyphosate can increase the expression levels of NPQ regulatory genes Psb S,VDE,and ZEP.The target gene of LHCB7 mutant interacts with NPQ-related genes Psb S and LHCSR differently,indicating that this interaction mediates NPQ involved in regulating plant response to hormesis effect.In summary,glyphosate hormesis effect can significantly stimulate plant growth and can be used to ensure agricultural safety and production.This study further elucidated that LHCB7 gene is involved in regulating this effect.The research results will provide theoretical basis for the scientific and rational use of glyphosate and technical support for the application of hormesis effect in agricultural safety and production.