Mechanisms Of Glyphosate-induced Male Sterility In Sea Island Cotton Based On Transcriptome Analysis

Glyphosate is the most widely used herbicide in production,and Sea Island cotton is an important raw material in high-grade cotton textiles.The application of glyphosate-resistant Sea Island cotton in production will promote the mechanization of chemical weed control in sea island cotton;meanwhile,male defeat will occur under suitable glyphosate concentration treatment,and male sterile lines can be obtained,and the use of excellent male sterile lines will promote the preparation of hybrids.In this study,we set four concentrations,3.75 g/L,7.5 g/L,15 g/L and 30g/L,to study the changes of growth and development of Sea Island cotton and male sterility phenomenon under different concentrations using the new long cotton 5 line as material,and the main conclusions are:1.15 g/L glyphosate is the appropriate concentration for chemical staminicideGlyphosate treatment has a large impact on leaves,which will lead to a decrease in leaf SPAD values,thus affecting photosynthetic capacity and chlorophyll fluorescence,and will lead to a complete loss of leaf green when the concentration exceeds 15 g/L.As fertility progresses,leaves will gradually re-green and resume normal growth.The decrease of chlorophyll caused by glyphosate in Sea Island cotton caused its photosynthesis to be affected,in which Pn,Tr,Gs,Fv/F0,Fv/Fm all showed a decreasing trend,while Ci showed an increasing trend,and all of them gradually returned to normal at the later stage.The recovery time was greatly delayed after exceeding 15 g/L.Meanwhile,with the increase of glyphosate treatment concentration,the results of both years showed that the relative indexes of agronomic traits decreased and the growth was suppressed,and the plant height,stem thickness and leaf stage of each treatment gradually recovered with time.Glyphosate treatment would have a great effect on the mangiferous acid pathway,and the specific pattern was that the higher the concentration,the higher the expression of CP4-EPSPS gene,and the higher the concentration of EPSPS synthase produced by it,but due to the low concentration of glyphosate,it made the accumulation of mangiferous acid also increase with the increase of glyphosate concentration.Among them,30 g/L was the highest accumulation of mangiferic acid.The result data of hybridization experiment showed that 15 g/L glyphosate treatment concentration could be used for normal preparation of male sterile lines,and more than 30 g/L would lead to a rapid decrease in the rate of boll formation.It is recommended to use 15 g/L glyphosate for the preparation of hybrids in production.2.Glyphosate causes male sterility in Sea Island cotton by disrupting hormone metabolismGlyphosate inhibits the development of organs in Sea Island cotton,and the inhibitory effect becomes more pronounced with higher glyphosate concentrations,as evidenced by smaller flowers,shorter filaments,crumpled anthers,and aborted pollen,and the higher the concentration,the more pronounced the phenotype.Histological studies showed that the key period affecting anther abortion caused by 15 g/L glyphosate was the tetrad period,which corresponds to bud length of 8-9 mm,as shown by abnormal separation of tetrads,early disintegration of the fleece layer,cavity of microspores,and irregular shape.15 g/L glyphosate and CK results of mangiferous acid gene expression in different tissues showed that it was due to the higher expression of CP4-EPSPS gene expression was higher in the ovary and lower in the anther,so it would cause male sterility and normal female organs.Transcriptomics revealed a total of 3042 differential genes in 15 g/L glyphosate treatment compared to CK,most of which were located on chromosomes D05,D11,and A05,with the highest number of differential genes in 8-11 mm buds among different bud lengths,and this result was consistent with the histological observations.GO enrichment analysis showed that the components highly enriched with biological components were KEGG enrichment indicated that glyphosate affected various metabolic pathways such as hormone signaling and abscisic acid response during anther development.The most reliable pathway for the enrichment of genes in the transcriptome results was found to be plant hormone metabolism,and this was confirmed by the determination of growth hormone,abscisic acid,cytokinin,gibberellin,and jasmonic acid by high performance liquid chromatography,with the abscisic acid content.It is the disruption of hormone levels that leads to abnormal anther development and male abortion.