Effect Of UDP-glucose Pathway In Pectin Synthesis On Cotton Fiber Development

Pectin has a fundamental role in primary cell walls,and affecting secondary wall thickening in fiber and woody structures.And the pectin is a polygalacturonic acid complex polysaccharide formed by polymerization of UDP-?-D-galacturonic acid(UDP-GalA).So the UDP-GalA is an important precursor for pectin synthesis,and it is biosynthesized through the D-galacturonate,myo-inositol,and UDP-glucose pathways.However,the detailed mechanism is still unclear in upland cotton(Gossypium hirsutum).Metabolomic data found that with the development of fiber,the content of each pectin precursor ribose showed a downward trend.The content of each pectin precursor ribose in the upland cotton varieties 0-153 with excellent fiber quality is significantly lower than that of low fiber quality sGK9708.It is speculated that these pectin precursor ribose may play an important role in the formation of cotton quality.In this paper,we screened the expression patterns of putative gene family members involved in pectin biosynthesis by re-analyzing transcriptomic data.A total of 52 genes were identified in upland cotton(Gossypium hirsutum).The expreesion patten was verified by qRT-PCR assay.In order to further screen for substances that promote fiber elongation,the pectin precursor ribose material was applied to the ovule medium,and it was found that UDP-?-D-glucuronic acid(UDP-GlcA)and UDP-?-D-glucose(UDP-Glc)can significantly promote fiber elongation and promote the expression of related genes.,while the addition of other pectin nuclear sugar precursor substances had no obvious effect on the growth phenotype of ovule.UDP-Glc and UDP-GlcA are two key precursors in the UDP-glucose pathway,it is speculated that the UDP-glucose pathway may play an important role in the synthesis of upland cotton pectin.The UDP-glucose dehydrogenase(UGD)is the starting enzyme of the UDP-glucose pathway,which may play an important regulatory role in this pathway.Bioinformatics analysis of the UGD gene family revealed that the gene family has a conserved motif and gene structure.Combined with the transcriptome data,we found that the gene GhUGD10 has different expesion level during the fiber development,the subcellular localization revealed that the GhUGD10 protein was mainly expressed in the cell membrane.An arabidopsis overexpression vector was constructed for the GhUGD10 gene,and showed that the roots of the transgenic lines increased significantly compared with the wild type.It is speculated that GhUGD10 is related to cell elongation and may promote cotton fiber cell protrusion and elongation.