Cytological Observation And Transcriptome Study On Different Developmental Stages Of Watermelon Male Flowers

Watermelon(Citrullus lanatus),which is an annual herb belonging to Cucurbitaceae is a monoecious plant.According to a Chinese agricultural data,as the most important summer refreshing fruit and the main resource of people's income,whose planting area in 2017 was 184,8700 hectares and the output reached 7927.63 million tons.In order to improve the comprehensive characters,such as yield and quality of watermelon,it is necessary to study some contents related to the growth and development of watermelon through various ways.During the growth and development of watermelon,plant fertility,seed setting rate and fruit quality are closely related to male flowers' development.Therefore,the research related to male flowers' development provides a theoretical basis for improving the economic benefits of watermelon and carrying on dominant cross breeding.The experiment used the non-flowering flower buds above the flowering node of the watermelon variety 'Xinteda Zhengkang 9' as the experimental material,and used microscopic observation by acetic acid magenta staining,DAPI staining and Carbo red staining to distinguish the different developmental stages of anthers.Transcriptome sequencing analysis of anthers at different developmental stages,screening for genes related to anther development,and binding to metabolic pathways to verify related genes.The test results are as followings:1.Through the observation of anthers in pollen mother cell stage,tetrad stage,mononuclear stage,binucleary stage and mature stage by acetic acid magenta tableting,Carbo magenta tableting and DAPI tableting,the results showed that acetic acid magenta tableting method is superior to the other two tableting methods.2.The longitudinal and transverse diameters of the unopened male flower buds of watermelon were measured.The cytological observations of different developmental stages of pollen showed that the pollen grew from the tetrad to the mature stage,and the longitudinal and transverse diameters of the flower buds increased.There is a very significant difference between the length and length of the male flower buds in different periods3.The transcriptome sequencing of anthers in the four periods:tetrad,mononuclear,dinuclear and maturity and the results are as following:firstly,there were 16288 differentially expressed genes in four periods,and there are 2014 differential genes in the tetrad and mononuclear periods,including 753 up-regulated genes and 1261 down-regulated genes.Secondly,there are 3529 differentially expressed genes in the tetrad and dinuclear stages,including 1381 up-regulated genes and 2148 down-regulated genes.Thirdly,there were 4628 differentially expressed genes in maturity,including 2082 up-regulated genes and 2546 down-regulated genes.Fouthly,there were 1490 differential genes in mononuclear and dual-nuclear stages,including 634 up-regulated genes and 856 down-regulated genes.There are 3495 differential genes in the mononuclear stage and maturation periods,including 1708 up-regulated genes and 1787 down-regulated genes.Finally,there are 1132 differential genes in the two-nuclear and mature stages,including 45 genes up-regulated and 681 genes down-regulated.4.The KEGG and GO enrichment analysis of differential genes showed that the metabolic pathways mainly included Starch and sucrose metabolism?Phenylpropanoid biosynthesis?Nitrogen metabolismand Plant hormone signal transduction.Transcriptome expression regulation analysis combined with qRT-PCR analysis identified 24 genes which may play important regulatory roles in pollen development.