Analysis Of Ginkgo Trumpet Leaf Mutant And Evolution Of Leaf Adaxial-abaxial Development Regulatory Genes

Leaf is the plant's organ to harvest solar energy and absorb carbon dioxide,which largely determines its photosynthesis rate and therefore its capability to adapt to the environment.Megaphyll plants appeared in the Devonians 360 Million years ago,their high photosynthesis rate made them stand out and dominate the whole terrestrial biosphere.Thus the study of leaf shape has always been a hot topic in plant evo-devo and agricultural sciences.The current study on leaf shape mainly focuses on the medial-lateral,proximal-distal and adaxial-abaxial development.The adaxial-abaxial development is considered to be most important,since mutations could lead to the rolling of leaves,which largely reduces the solar-absorption area and which in worse cases could lead to mortality.This study is based on Ginkgo natural mutants with trumpet-form leaves and aims to analyze the gene differential expression patterns of the leaf adaxial-abaxial development regulatory genes in the mutant and wild type,which fills the blank in the research area of gymnosperm leaf form development.RNA-seq data of ginkgo mutant buds and wild type were analyzed using hisat2,stringtie and edge R.As a result 3569 significantly differential-expressed genes were found,these were further screened by volcano plotting with |log2Fold Change| > 1 and –log2Pvalue > 100 as standards,which lead to a final differentially expressed gene group of 399 genes.These genes were further analyzed using GO enrichment and KEGG pathway analysis.Afterwards,gene expression level changes in buds of Ginkgo mutant and control group of master regulators of the leaf adaxial-abaxial development gene regulation network,ARF3,ARF4,AS1,KANADI1,YABBY5,PHABULOSA,PHAVOLUTA,REVOLUTA,were analyzed using RNA-seq data.Gene expression level changes in leaves of 8 kinds of Ginkgo mutants(single trumpet,single needle,double trumpet,double needle,trumpet & needle,unfolded & trumpet,unfolded & needle and biparted)and control group of master regulators of the leaf adaxial-abaxial development gene regulation network were analyzed using RT-PCR data.This study shows the overall over-expression of genes in charge of leaf abaxial development in ginkgo trumpet shape leaf mutants and lays foundation for further studies on leaf adaxial-abaxial development in gymnosperms.Furthermore,this study analyzed the gene copy number and gene structures of ARF3,ARF4,AS1,KANADI1,YABBY5,PHABULOSA,PHAVOLUTA,REVOLUTA homologs in Physcomitrella patens,Selaginella moellendorffii,Ginkgo biloba,Picea abies,Pinus taeda,Populus trichocarpa,Amborella trichopoda and Oryza sativa,which views the leaf adaxial-abaxial development gene regulation network as a whole system to study its evolution from bryophytes to lycophytes and then to gymnosperms and angiosperms.This study proposes the hypothesis that the most recent common ancestor of gymnosperms should have needle-shaped leaves and lays foundation for deeper understanding in the evolution of the leaf adaxial-abaxial development gene regulation network.