Mineral stress response of Vitis cell wall transcriptome: identification, characterization and expression of genes from key families involved in wall biosynthesis and modification

Doutoramento em Engenharia Agronómica - Instituto Superior de Agronomia - UL

Grapevine (Vitis vinifera L.) is one of the most economically important fruit crops in the world. Abiotic stresses are likely to affect the plant development, yield and ultimately the quality of economic products. The cell wall (CW) is a dynamic structure that determines plant form, growth and response to environmental conditions. To investigate V. vinifera CW adaptative response to restrictions in major nutrients, essential to plant growth and development, N, P and S were excluded from V. vinifera callus and shoots growing substrates. Water stress on berry skin CW was studied in non-irrigated versus irrigated plants of two varieties. Specific CW components, namelly cellulose, were impacted in callus, shoots and berries subjected to abiotic stress. To overcome this, V. vinifera CWs suffered compositional changes and reorganization of deposition of several CW components, in particular the degree and pattern of pectin methyl-esterification, arabinan and XyG, which together promote stiffening of the CW. Moreover, polysaccharides of callus grown under mineral deficiency, mainly N, were more tightly bound in the CW. Under mineral stress the expression of genes from CW candidate enzyme families was affected for example downregulation of GH9C, XTHs with predicted hydrolytic activity and PMEs were observed. In shoots probed with CW-epitope monoclonal antibodies an increase in pectins with a low degree of methyl-esterification able to dimerise association through calcium ions was observed. CWs grown under N deficiency were enriched in 1,5-arabinan rhamnogalacturonan-I (RG-I) side chains. The impact on CW was dependent on the mineral stress, nitrogen leading to more pronounced responses, supporting the primary role of this major nutrient in plant development and metabolism. Water shortage affected berry skin by stiffening the CW, probably due to alterations in PGs, XTH and PME expression and pectin methyl-esterification in a variety dependent way