ABSTRACT: The molecular mechanisms underlying cell wall biosynthesis are poorly understood. In this study, microscopic analysis showed that protoplasts generated a new cell wall within 48 h after transfer to a wall-regeneration medium. To identify genes related to cell wall biosynthesis in cotton, suppression subtractive hybridization was used to visualize differential gene expression at seven time points within the first 48 h. In total, 412 differentially expressed sequence tags (ESTs; >3-fold) were identified, and 210 unigenes were sequenced successfully. As confirmed by reverse-transcription PCR (RT-PCR) and real-time quantitative reverse-transcription PCR (QRT-PCR) analysis, the selected genes displayed complex expression patterns during cell wall regeneration from protoplasts and included most previously published cell-wall-associated genes. ESTs similar to cell-wall-protein genes, such as proline-rich protein (PRPL), glycine-rich protein (GRP), extension (EPR1), fasciclin-like arabinogalactan protein (FLA2), and expensing-like protein (EXLA and EXLB), which might participate in primary cell wall or secondary cell wall construction and modification, were up-regulated during cell wall regeneration from protoplasts. Sucrose synthase, an important enzyme in the sugar signalling pathway, played important roles in cellulose biosynthesis. Our findings also highlighted the function of some transcription factors during cell wall regeneration from protoplasts, including the squamosa promoter binding protein-like 14 (SPL14), NAC, Gbiaa-re, MYB, WRKY, swellmap 1 (SMP1), RAD5, and zinc finger family protein, as well as the enrichment of Ca(2+)-calmodulin signal molecules. On the basis of the gene expression profiles, a model of cell wall regeneration from protoplasts derived from cotton suspension cultures is proposed.
