Whole-Transcriptome Regulation Of Heteromorphic Leaf Development In Populus Pruinosa

Populus pruinosa belongs to Salicacea and is a dominant tree species growing in extremely arid desert and semi-desert environments.The leaf shape of adult poplars is oblong,round and broad from the base of the crown to the top.However,the molecular regulatory mechanisms involved in leaf function and leaf shape change of heteromorphic leaves in Populus pruinosa remain unclear.In this study,the oblong,round and broad leaves of adult Populus pruinosa at mature leaf age were selected as the research objects,and the leaf shape structure,physiological characteristics,expression characteristics of full transcriptome were analyzed.(1)By studying the morphological characteristics of the three kinds of heteromorphic leaves,it was found that the number of trichome structures,stomatal density and photosynthetic rate increased gradually from oblong to broad leaves.It was speculated that Populus pruinosa could cope with the desert environment with less precipitation and strong light by reducing leaf temperature,avoiding excessive transpiration and water loss,and controlling light absorption.In addition,the vascular bundle sheath and mesophyll palisade tissue of broad ovate leaves are more developed,which may be the reason why the broad ovate leaves distributed in the crown of Populus pruinosa and have stronger light adaptation and water transport ability.Therefore,the broad and round leaf structure of poplars provides more stable energy supply and environmental adaptability.(2)Full transcriptome sequencing of the three heteromorphic leaves of Populus pruinosa showed that m RNA and non-coding RNA(mi RNA,circ RNA and lnc RNA)expression levels changed dynamically from oblong to broad leaves.A total of 1073 differentially expressed m RNAs were identified in three comparison groups of round vs oblong leaves,broad vs oblong leaves and broad vs round leaves of Populus pruinosa heteromorphic leaves.Among them,the up-regulated expression of genes in broad leaves and round leaves(" wide leaves ")compared with oblong leaves(" narrow leaves ")was mainly related to photosynthesis,oxidoreductase activity and cellulose synthase activity.These genes may be involved in the photosynthetic process and the regulation of leaf cell structure to influence the functional establishment of Populus pruinosa wide leaf.It is noteworthy that the differential m RNAs contain members of the transcription factor family for leaf morphological development such as TCP,YABBY and PIN.Direct homology comparison with Arabidopsis thaliana showed that At TCP7,At TCP9,At TCP14,At YABBY1,At YABBY2,At PIN3,which suggested that these genes may be involved in the regulation of leaf morphology and development of heterologous leaves of Populus pruinosa.In addition,a total of 41 differentially expressed mi RNAs were identified in broad leaves compared with narrow leaves,including mi R156,mi R169 and mi R319,which have been reported to be involved in leaf development.52 differentially expressed lnc RNAs and 42 circ RNAs were identified.The functions of mi RNA target genes are mainly related to catalytic activity,ethanol metabolism and small molecule biosynthesis.The functions of lnc RNA target genes are mainly related to photosystem,photosynthesis and response to stress.The functions of circ RNA target genes are mainly related to oxidoreductase activity,response to extracellular stimuli and biological regulation.By constructing m RNA and non-coding RNA regulatory networks of heteromorphic leaves in Populus pruinosa,we found that the m RNA expression in Ppr TF01G3401-ptc-mi R397a-novel＿circ＿0002338;Ppr TF15G1168-ptc-mi R397anovel＿circ＿0002338;Ppr TF09G0404-ptc-mi R156a-novel＿circ＿0000352;Ppr TF04G1095-ptc-mi R6430-LNC＿003350-novel＿circ＿0000500 regulatory network was up-regulated in "wide leaves" compared with "narrow leaves" and was significantly enriched in morphogenesis,regulation of stimulus response,chlorophyll a oxygenase activity and oxidoreductase activity.These regulatory networks may be involved in the regulation of leaf shape,photosynthetic response and response to stress.In addition,a novel＿circ＿0000352-TCP4-novel＿186 regulatory network containing the leaf phenotypic development gene TCP4 was also found.Therefore,non-coding RNAs may be involved in the regulation of phenotypic and functional development of heteromorphic Populus pruinosa leaves.(3)To further understand the role of TCP in the regulation of Populus pruinosa leaf shape,the TCP gene family was further identified in this study 33 non-redundant PpTCPs were identified in the genome data of Populus pruinosa at the chromosome level.Genome-wide replication event/fragment repetition was the main driver of TCP gene family expansion in Populus pruinosa.In addition,TCP4,TCP7,TCP19 and TCP27 were differentially expressed in heteromorphic leaves.Combined with the morphological characteristics of different heteromorphic leaves,this study speculated that PpTCP4 and PpTCP19 might affected the morphogenesis of " narrow leaves"(oblong leaves)of Populus pruinosa by participating in the regulation of leaf cell division.PpTCP7 and PpTCP27 may be involved in the regulation of "wide leaves" of Populus pruinosa by promoting cell expansion and regulating petiole length.The results of this study provide a theoretical basis for the whole-transcriptome regulation of functional and phenotypic changes in heterologous leaves of Populus pruinosa.