The invention discloses a full-length sequence of a new cotton 
fiber specific 
expression gene GhDUF231L1, of which a function relates to formation and modification of cotton 
fiber secondary wall materials. The GhDUF231L1 
gene comprises five exons and four introns as well as a 1.6kb 
promoter fragment and an encoded 430 
amino acid. The 
gene is a cotton 
fiber secondary wall development specific 
gene, of which the expression quantity is rapidly increased in fibers after flowering for 15 days and the expression quantity reaches a 
peak value after the flowering for 20 days. The GhDUF231L1 
promoter mainly expresses in a vascular 
system of leaf veins and stems of transgenic 
arabidopsis thaliana leaves and also expresses in roots, flowers and legumes; a 
promoter area contains a cis-acting element which can be bonded with upstream transcription factors. Transgenic plants are enlarged, the 
cellulose content is increased and the contents of 
cell wall 
monosaccharide compositions are changed because GhDUF231L1 is over-expressed in 
arabidopsis thaliana. The results prove that GhDUF231L1 participates in 
plant growth, in particular to the biological synthesis of secondary 
cell walls, so that GhDUF231L1 possibly plays a key role in cotton fiber development.