Pectins: Transcriptomic analysis of genes involved in their synthesis and modifications during barley seedling development

Plant cell walls are the strengthening constituent of plant cells and are composed of cellulose microfibrils cross-linked by hemicelluloses and embedded in a pectin matrix. Pectins, one of the groups of polysaccharides in the cell walls, are galactronic-acid rich heterogeneous polysaccharides with high degrees of complexity and substitutions. Among the functional richness, pectic polysaccharides are usually associated to the growth, defence, and control of cell wall porosity. Compared to dicots which have around 35% of pectin content in their cell walls, they are found at much lower abundance in commelinid monocots, around 2-10%. Pectins are assumed to be functionally replaced in monocots by other polysaccharides such as glucuronoarabinoxylans which also contain a large number of glucuronic acid monomers. Despite the minority of pectic polysaccharides in monocot cell walls, monocot genomes have large numbers of genes that are potentially involved in pectin biosynthesis and modifications, strengthening the importance of pectin during growth and development.

During germination of a barley seed, the coleoptile chaperons the true leaves to the surface of the soil. Coleoptiles are excellent platforms to examine cell growth and development since they are non- photosynthetic rapidly growing tissues, and their mRNA pools contain a larger percentage of genes involved in cell wall synthesis. Among numerous importance’s of plant cell walls, their synthesis and modifications are closely linked to growth of plant cells, thus development of the plant tissues. As the coleoptile cells are rapidly growing, cell wall synthesis and modifications are tightly controlled at transcriptomic level. Thus, analysis of pectin associated genes during the barley coleoptile development hints the importance of role of pectins and how they are modified during early development. Understanding transcriptomic control contributes to knowledge of in muro metabolism and roles of transcripts for the seedling growth and adaptation. In this project we have completed transcriptomic analyses of coleoptile tissues from initiation to 3 days after termination of growth. The number, abundance, and coexpression analyses of genes involved in pectin biosynthesis in barley coleoptiles will be discussed.

Audience Takeaway:

• The talk will enlighten the roles of putative pectin-related genes during barley seedling germination and development.
• Understanding pectin synthesis and modifications during coleoptile growth will be useful for understanding cell wall biology during growth.