The Morphological Characteristics And Transcriptome Expression Of Cleistogamy In Cleistogenes Songorica

Cleistogenes songorica has two types of reproductive system,chasmogamy(CH)and cleistogamy(CL)which is a perennial,xerophytic herb.It can be used as an excellent turfgrass and ecological grass,with the characteristics of high feed value,drought and cold resistance..So far,the information about the morphological and transcriptomic of CL in C.songorica is still limited,which severely limits its genetic breeding and seed production studies.In this study,the flower organs from two different types(CH and CL)were studied on the different flower development stages,flower structure,lodicules,pollen morphology and flower-related genes by morphological and anatomical investigation,frozen section,scanning electron microscopy and transcriptome sequencing.The main results were as follows:(1)According to the microstructural characteristics,the development of CH floret was divided into five stages: floret primordium,white anther,green anther,yellow anther and purple anther(flowering stage).However,CL floret included floret primordium and different developmental stages at the white anther stage.Both CH and CL flowers were composed of 1 lemma,1 palea,2 lodicules,3 stamens and 2 feather-like stigmas.The anther of CH flower was 4.4 times longer than CL flower,while the filament length of CH was significantly smaller than CL flower.The first and second lodicule of CH flower were 1.58 and 2.25 times thicker than the CL flower,respectively.The pollen grain of CH and CL was single-grained with alone apertune.The shape of CH pollen grain was oblate.the length of polar and equatorial axis was(18.33 ± 1.82)?m and(16.67 ± 2.02)?m respectively.Exine sculpture was smooth.The shape of CL pollen grain was prolate,and the length of polar and equatorial axis was(28.26 ± 1.31)?m and(17.56 ± 1.3)?m.Exine sculpture was grainy.(2)A total of 69,331 unigenes were generated from CH and CL flowers assembly.15,782 unigenes were specifically detected in CH samples and 12,892 in CL samples.Differentially expressed genes(DEGs)analysis revealed 18,336 unigenes.801 flower-related genes were identified,which included 589 unigenes in the GO database.Among them,432 unigenes were associated with flower development,114 unigenes were related to photoperiod,and 43 unigenes were associated with flower morphology.The qRT-PCR assays were implemented to verify the top 9 homologous cleistogamy unigenes.Unigene CL1597.Contig1_A11,CL1597.Contig2_A11,CL1597.Contig3_A11,Unigene6273_A11,CL9616.Contig2_A11 and CL9616.Contig3_A11 were up-regulated.Unigene 10198_A11 and CL1597.Contig4_A11 were down-regulated in CL flowers.