Abstracts Category : Other

Cellulose content variation and underlying gene families in bread wheat

by Simerjeet Kaur

Synthesis and remodelling of various cell wall components play a vital role in plant development, architecture and innate immunity. Plant cell walls are mainly composed of cellulose and hemicellulose which produce a bulk of renewable biomass vital for food, feed and biofuels. Cellulose in the primary and secondary cell wall of plants is synthesised by the family of genes called CesA (Cellulose synthase A). This study is a first report about the distinctive structural and functional motifs of primary and secondary cell wall synthesis genes. Using publicly available genomic databases and resources, 22 TaCesA genes located on A, B and D genomes of hexaploid wheat were identified. Cellulose in secondary cell walls is synthesised by three genes (TaCesA4, TaCesA7, and TaCesA8) co-expressing in the mature stem tissues of bread wheat. But the relative transcript abundance was found to be higher for TaCesA4 genes, which indicates its major role in the secondary cell wall cellulose synthesis. We employed the virus-induced gene silencing (VIGS) approach to functionally characterize TaCesA4 gene through silencing its three homoeologs (TaCesA4A, TaCesA4B, and TaCesA4D) collectively in bread wheat. Silenced plants showed a significant reduction in transcript abundance and cellulose content in the stem tissues. However, the anatomy of stem cross sections of silenced plants did not show any evidence of abrupt changes in the secondary cell wall of stems at the booting stage. A panel of 265 diverse wheat lines was evaluated for natural variation of cellulose content that was linked to the SNP genotyping data through genome-wide association studies (GWAS). This analysis led the identification of novel genes (-tubulin and UDP-glycosyl transferase) associated with cellulose biosynthesis in wheat. In addition, Cellulose synthase-like (Csl) genes of wheat were explored. These genes have been known for the regulation/synthesis of hemicelluloses such as heteromannan, xyloglucan, heteroxylans, and mixed-linkage glucan. A total of 108 Csl genes were identified based on the family specific Pfam conserved domains. Tissue-specific expression and phylogeny of Csl genes were also elucidated. Taken together, genome- wide exploration of CesA & Csl genes and their association with cellulose and hemicellulose biosynthesis offer a valuable resource for designing high yielding wheat varieties possessing appropriate lignocellulosic traits. La synthse et la remodelage des divers composants des parois cellulaires jouent un rle important dans le dveloppement, l'architecture et l'immunit inne des plantes. Les parois cellulaires sont principalement composes de cellulose et d'hmicellulose, lesquelles reprsentent une quantit importante de biomasse dans les aliments pour humains et btail autant que dans les biocombustibles. La cellulose prsente dans les parois cellulaires primaires et secondaires est synthtise par des gnes de la famille CesA (Cellulose synthase A). Cette tude est la premire dcrire les motifs structurels etAdvisors/Committee Members: Jaswinder Singh (Supervisor).