Mapping The Allocation Pattern Of Plant Biomass Through A Composite-trait Analysis

Biomass allocation is a process by which a plant allocates a limited amount of energy to its developing organs to maximize its success for survival,growth,and reproduction.The study of how a plant optimizes its biomass allocation is of utmost significance in both evolutionary biology and agriculture.Despite an important role of genes in mediating this process,the detailed genetic architecture mediating biomass allocation is still poorly understood.In this study,I designed a QTL mapping experiment to identify whether there exist a set of specific QTLs responsible for biomass allocation and how these QTLs guide plants to allocate their biomass to different organs.The experiment includes 85 genotyped recombinant inbred lines(RILs)derived from two morphologically contrast ecotypes of Arabidopsis thaliana,LER and SHA,planted in a randomized block design.The total biomass of each RIL is partitioned into root,stem,and leaf components.I implemented a composite mapping model to genome-wide scan whether QTLs determine the proportion of biomass allocation into different organs.I also deployed a dynamic model to predict the biomass allocation of the adult plant using developmental trajectories of leaf number per unit plant height.These analyses produce the following results:(1)The composite mapping model identified a set of QTLs for biomass allocation into different organs;i.e.,59 for the root,53 for the stem,and 67 for leaves.Among these QTLs,eight affect the allocation proportion of all organs,suggesting that they are pleiotropic QTLs.Gene GO enrichment analysis indicates that most of the significant QTLs detected reside in the candidate genes for biomass accumulation and leaf growth,such as SNP40716-40719 in the region of the Ha HB11 gene and SNP51094 in the region of the NF-YA10 gene.Plants that carry genotype CC at this SNP 51094 tend to allocate more biomass into rosette and stem than those with genotype GG.(2)The dynamic model identified 203 significant QTLs,distributing on chromosomes 1,3,4 and 5,which determine the association of leaf numbers at different developmental stages with biomass allocation.A SNP 527485,closed to gene Os EXPA8,plays multiple roles in the growth of plants,such as improving root structure,plant height,leaf number and leaf area.In conclusion,applying the composite trait mapping model to the Arabidopsis RILs data,this study analyzed plant biomass allocation patterns and discovered some key genes that are significantly related to them.The results are potentially being useful for exploring the genetic mechanisms of plant allocation strategies in response to resource and environmental changes.