| Cotton is one of the most important economic crops in the world.Because of its growing environment temperature is relatively high,so in tropical and subtropical areas planted more.Cotton fiber is a raw material for textiles,papermaking and other industries,so it has a high economic value.Cotton fiber is the result of a high degree of growth and thickening of the unicellular protuberances of the outer epidermis.The cellulose content of mature cotton fiber is as high as 90%or more.Therefore,cotton fiber is a model system for studying cell elongation and secondary wall synthesis.The development of cotton fiber is divided into four stages,the initial stage that affects cotton fiber density,the elongation stage that affects the length of cotton fiber,the secondary wall thickening stage that affects the quality of cotton fiber,and the last stage is the dehydration and maturation stage.Our laboratory has isolated and cloned a type ⅡKNOX gene GhKNL1 from the cotton genome.Previous experiments showed that the gene was highly expressed during the secondary wall thickening stage,affecting the secondary development of cotton fiber cells,but it’s unclear how the gene functions exactly.This study further explored the regulatory role of GhKNLl on downstream target genes,revealed the regulatory mechanism of the transcription factor,and provided a theoretical basis for the improvement of cotton fiber quality and yield.The main findings are as follows:1.Phenotypic analysis of offspring lines(T2 and T3 generation)of GhKNL1 transgenic cottonThe phenotypic analysis of RNA interference(RNAi)and dominant repression(DR)of transgenic cotton T2 and T3 generations revealed that the length of mature cotton fiber in RNA interference transgenic cotton was significantly higher than that of wild type(WT),and the cotton fiber length of dominant suppression transgenic cotton was significantly shorter than that of WT.18DPA,27DPA,30DPA,33DPA cotton fibers were embedded in LR White resin and paraffin.The shape,size,and cellulose content and secondary wall thickness of the cross section of the fibroblasts were observed and found.Compared with WT,the cotton cell wall thickness of GhKNL1 RNAi transgenic cotton increased.However,the cotton cell wall thickness of GhKNL1 DR transgenic cotton was thinner than that of WT.And the morphology of cotton fiber cells of transgenic cotton was shrunken and deformed.These phenotypes demonstrate that GhKNL1 transcription factors play a negative regulatory role in cotton fiber development.2.The cellulose content in the cell wall of GhKNL1 RNAi transgenic cotton fiber is incressedSlice observations showed that the cell wall thickness of the transgenic cotton fibers changed,while more than 90%of the cell wall components of mature cotton fibers were cellulose,and the remaining was hemicellulose and lignin with very low content.The cellulose in mature cotton fibers was extracted using the anthraquinone sulfate method,and the cellulose content of RNA silencing transgenic cotton was found to be significantly higher than that of the wild type.Acetyl bromide extraction of lignin from mature cotton fibers revealed no significant change in transgenic cotton compared to wild type.It is further illustrated that GhKNL1 may affect the deposition of cellulose during secondary wall development.3.Transcriptome analysis of GhKNL1 RNAi transgenic cottonTo further investigate the regulatory mechanisms of GhKNL1,we used transcriptome sequencing to find genes that are differentially expressed in RNA interference and wild-type 18DPA fibers.A total of more than 1000 differential genes were found under a screening condition with a pval... |
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