Genetic Dissection Of How Planting Density Impacts Leaf Allometry In Arabidopsis

Leaf is an important organ to maintain plant growth and development,and has strong plasticity to environmental changes.Density is an important environmental factor affecting plant growth.It plays an important role in determining the size and shape of plant leaves by influencing canopy light intensity,spatial distance and individual competition.Previous studies on plant leaf density response have been carried out from the aspects of plant shade syndrome,light regulation pathway,plant immunity,etc.these studies have found the function of genes affecting density induced leaf phenotypic plasticity.However,the leaf is a complex organ,its physiological function is not only affected by its size,but also by its morphological structure,and more controlled by the leaf morphological allometric growth mode.However,how density affects the allometric growth of leaves and how this effect is regulated by genes is an important biological problem,and the research on it is quite weak,lacking in-depth analysis.In this study,we used the mapping population of Arabidopsis recombinant inbred lines to systematically analyze the genetic structure of the effect of density on leaf size morphological allometric growth from the perspective of quantitative genetics.We found the important QTLs affecting leaf length leaf area and petiole length leaf length,systematically studied the effect of density on these allometric QTLs,and constructed the allometric QTL interaction network.The results are as follows:(1)A checkerboard card was designed as the spatial reference frame for leaf photographing,so that leaf morphology could be tracked in any appropriate photo pose under non-in vitro conditions,and an absolute quantitative phenotypic and morphological characteristics of leaves could be obtained through subsequent 3D morphological reconstruction of leaves.Therefore,this method is a reasonable method to investigate the dynamic phenotype of leaf development and can achieve the characteristics of non-injury at the same time.(2)Leaf phenotypes under low and high density were analyzed by dynamic allometric models of leaf length and leaf area and petiole length and leaf length,respectively.Based on the Manhattan plot analysis of genome-wide SNP,309,293,54 and 140 QTLs were identified.Venn diagram analysis revealed that these QTLs could be further classified into trait specific,trait shared,trait specific and low density environment shared,etc.Among them,26 QTLs co-regulated the dynamic allometric development of leaf length-leaf area and petiole length-leaf length under low density.There were 40 QTLs that jointly regulated the dynamic allometric development of leaf length-leaf area and petiole length-leaf length under high density.There were 6 QTLs jointly regulating leaf length and leaf area under high and low densities.There was one QTL jointly regulating petiole length and leaf length under high and low density.Different QTLs showed the characteristics of one-factor pleiotropy and QTL-environment interaction.(3)The functional annotations of the above QTL can be summarized as follows: genes directly related to leaf development,circadian rhythm regulation,auxin response genes,leaf morphology determinants,immune-related disease resistance genes,photoreceptor regulation genes,and shade syndrome regulation genes.The first four are related to the regulation of leaf self-development,and the last two are related to the environment of plant response density differentiation.(4)Based on the analysis results of four sets of QTL mapping for allometric traits in two pairs of each pair at high and low density,the core regulatory genes of the four sets of data were mined through the construction of gene game network.Two or three key hinge genes were identified in each network,among which the key nodes regulating the dynamic allometry of petiole length to leaf length were identified at low and high density as TPR-like,ZIP5 genes,and the squares in/WD40 repeat like gene,transposon gene,antisense long non-coding RNA gene regulating cytochrome P450 gene,respectively.The key nodes regulating the dynamic allometric traits of leaf length and leaf area were identified as the leucorrhoid gene of phosphoglycerate mutase family and exovesicular subunit exo70 protein gene under low density.At NHX1 gene was established under the condition of high density,which was involved in the regulation of leaf epidermal cell number and leaf area size.