桑树光合作用转录组研究

Research on mulberry photosynthesis transcriptome

研究高产桑品种鄂桑1号(E1)和对照桑品种湖桑32号(H32)光合特性及光合相关基因表达变化,为桑树高光效育种以及种质资源筛选提供理论依据。利用LI-6400XT型便携式光合测定仪测定桑树叶片气体交换和叶绿素荧光参数,同时测定叶绿素含量和1,5二磷酸核酮糖羧化酶(RUBP)活性,在桑树光合日变化曲线峰值和谷底取样进行转录组测序,比较不同桑品种光合相关基因表达的差异。对E1和H32的光合日变化测定结果显示,桑品种E1叶片的Pn峰值显著大于H32峰值(P<0.05),H32叶片Tr峰值显著大于E1峰值(P<0.05);不同品种桑树叶片Pn-PAR和Pn-Ci的响应中,CE、CSP为E大于H32,AQY、LCP、LSP、CCP为H32大于E1。E1在较弱光强下实现光合产物积累的能力强于H32,E1对CO2低浓度的利用效率优于H32;不同桑品种叶片叶绿素荧光参数中,E1叶片ΦPSⅡ和qP显著大于H32(P<0.05),H32的NPQ显著大于E1(P<0.05),表明H32叶片吸收的光能较多的以热能的形式进行耗散;H32的叶绿素a、叶绿素b和叶绿素含量均显著小于E1(P<0.05),E1的RUBP活性大于H32(P>0.05),表明E1光合能力优于H32。不同品种不同时段发现3356个差异表达基因(Differentially expressed genes,DEGs),代谢通路分析显示共有1136个DEGs注释到KEEG数据库,DEGs显著富集的光合作用相关代谢通路主要是光合作用固碳、碳代谢、卟啉和叶绿素代谢等3条光合相关代谢通路。在FC≥2且FDR<0.01的高差异表达基因中筛选功能描述与光合作用相关的新基因共10个。其中MulberrynewGene3646、MulberrynewGene1405、MulberrynewGene2419和MulberrynewGene320共4个DEGs可能是造成H32和E1净光合速率和产量差异的关键基因,可重点研究。

The photosynthesis characteristics and photosynthetic related gene expression of high-yield mulberry varieties Esang1(E1)and control mulberry variety Husang 32(H32)were studied to provide a theoretical basis for high-efficiency breeding of mulberry trees and screening of germplasm resources.Using LI-6400 XT mulberry leaf gas exchange and chlorophyll fluorescence parameters,chlorophyll content and ribulose carboxylase(RUBP)activity were measured simultaneously,transcriptome sequencing was performed on the peaks and valleys of mulberry photosynthesis curves,and the differences in photosynthetic related gene expression among different mulberry varieties were compared.The results of photosynthetic variation of E1 and H32 showed that the Pn peak of E1 leaves was significantly larger than that of H32(P<0.05),and the peak of Tr of H32 leaves was significantly larger than that of E1(P<0.05).In the Pn-PAR and Pn-Ci responses of different mulberry leaves,CE and CSP were E1>H32,AQY,LCP,LSP and CCP were H32>E1.The ability of E1 to achieve photosynthetic product accumulation under weaker light intensity is stronger than that of H32,and the utilization efficiency of E1 to low concentration CO2 is better than that of H32;among the chlorophyll fluorescence parameters of different mulberry varieties,ΦPSII and qP of E1 leaves were significantly higher than H32(P<0.05),and NPQ of H32 was significantly larger than E1(P<0.05),indicating that the light energy absorbed by H32 leaves was mainly dissipated in the form of heat energy;the chlorophyll a,chlorophyll b and chlorophyll content of H32 were significantly lower than E1(P<0.05),and the RUBP activity of E1 was higher than that of H32(P>0.05),indicating that the photosynthetic capacity of E1 was better than that of H32.3356 DEGs were found in different varieties and different time periods.The metabolic pathway analysis showed that there were 1136 DEGs annotated to the KEEG database.The photosynthesis-related metabolic pathways significantly enriched by DEGs were mainly photosynthetic carbon sequestration,carbon metabolism,porphyrin and chlorophyll metabolism.Photosynthetically related metabolic pathways.A total of 10 new genes related to photosynthesis were screened for highly differentially expressed genes with FC≥2 and FDR<0.01.The four DEGs,MulberrynewGene3646,MulberrynewGene1405,MulberrynewGene2419 and MulberrynewGene320,may be the key genes causing the difference in net photosynthetic rate and yield between H32 and E1,which can be studied intensively.