Photosynthetic responses mediate the adaptation of two Lotus japonicus ecotypes to low temperature

PABLO IGNACIO CALZADILLA; SANTIAGO SIGNORELLI; SANTIAGO J MAIALE; JORGE MONZA; OSCAR A. RUIZ

Congreso; SAIB - 51 Annual Meeting Argentine Society for Biochemistry and Molecular Biology / LI Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2015

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Photosynthesis is considered an important source of ROS in plants, and disruption of PSII activity may increase its production. This phenomena lead to photoinhibition, a process accelerated by cold stress. With the aim to address the photosynthetic acclimation response of L. japonicus under cold stress, two ecotypes (MG-1 and MG-20) were studied.Plants of 3-weeks-old were analyzed at different times (first, fourth and seventh day) of stress (5-9 ± 1 °C) and control (21-25 ± 1 °C) treatments. We have previously shown that photoinhibition occurs in stress and differentially between ecotypes, being MG-1 more affected than MG-20. In this study, we analyzed NADPH/NADP ratio and a reduction in NADPH was observed in the stress treatment, more intensively in MG-1 than in MG-20. D1 and D2 PSII protein contents were measured by immunoblots. While D1 protein contents remained constant, D2 turnover was evident. The relative expression of their corresponding genes was measured and did not explain immunoblots results. Superoxide dismutase (SOD) activity was addressed, and a contrasting response between ecotypes and treatments was observed, increasing more intensively in MG-20. As a conclusion, cold stress affects NADPH/NADP ratio differentially between ecotypes and increased SOD activity. Our results demonstrated a role of D2 protein in the acclimation response of L. japonicus to cold stress.