Underlying the mechanism of root growth inhibition by abiotic stress in root of Triticum aestivum L. (wheat) seedlings

LB PENA; RA BARCIA; CE AZPILICUETA; F BERRUEZO; MP BENAVIDES; SM GALLEGO

Buzios

Congreso; XIII Plant Physiology Brazilian Congress and XIV Latin American Meeting of Plant Physiology; 2011

Germination and postgerminative growth are critical events in the plant life. Any disturbance of the optimum environmental conditions can limit the growth or affect survival and/or productivity of plants. Abiotic stress is related to the generation of oxidative stress with the consequent production of oxidized proteins. In the present work we studied in which way growth parameters and cell cycle related genes and protein were affected by abiotic stress factors in root of Triticum aestivum L. (wheat). Treatments included metals (1 and 5 μM CuCl2, 1 and 10 μM CdCl2), 0.5 μM methyl viologen (MV), 1 mM H2O2 and water deprivation (22% polyethylene glycol, PEG), and were performed using a floating culture system, at 24±2ºC in darkness. Growth was evaluated by measuring the length of the primary root. Except for 1 μM Cu2+, the rest of the treatments decreased root length significantly. Except in seedlings treated with PEG, cross-sections through the meristem showed modification in the sizes and numbers of cortex root cells from the initials adjacent to the quiescent center up to the rapid elongation/differentiation zone. Cell death was not detected using Evans Blue staining. Water restriction increases root osmolyte content, measured as increase in conductivity and osmolarity. Total oxidized proteins were increased with metals, but total soluble and Ub-proteins contents were unaltered respect to control. Although cyclin D protein abundance in metal, PQ and H2O2-treated seedlings was similar to control, a decrease in Ub-cyclin and an increase in carbonylated-cyclin level with respect to control values was detected. The level of CDKD2 protein carbonylation was affected only by Cd and MV. Metal, PEG and MV increased root catalase activity inducing modification in the mRNA accumulation of CAT genes analyzed (cat1, cat2 and cat3). Different pattern in the level of expression of the genes related to the cyclinD/CDK2/Rb pathway was observed with the different treatments (PCNA, RDR, MCM2 genes). In conclusion, these observations suggested that the oxidative imbalance in the cell system could be responsible of the growth inhibition through carbonylation of specific cell cycle proteins during the metal treatment. More results are necessary to understand the relationship between drought and the decrease in seedlings growth.