Biochemical and physiological response of two Lotus japonicus ecotypes under low temperature conditions.

CALZADILA P.I.; SIGNORELLI S.; MAIALE S.J.; MONZA J.; RUIZ O.A.

FOZ IGUAZU

Congreso; 11TH INTERNATIONAL CONGRESS OF MOLECULAR PLANT BIOLOGY; 2015

SOCIEDAD DE GENÉTICA DE BRASIL

Lotus is an important genusof leguminosae, used as forage due to their high nutritional value andadaptability to marginal conditions for agriculture. However, its dry matterproduction is drastically reduced in coolest season. Thus, the acclimationresponse of two L. japonicus ecotypes(MG-1 and MG-20) was evaluated under cold stress. Plants of 3-weeks-old wereanalyzed during a stress (5-9 ± 1 °C) and control (21-25 ± 1 °C) treatment. Lightsaturating net photosynthetic rate (Asat)was measured and values were reduced for both ecotypes in the stress treatment,being MG-1 more affected than MG-20. Chloropyll fluorescence was also evaluatedand supports Asat results. ReactiveOxygen Species (ROS) and Reactive Nitrogen Species (RNS) were analyzed in theexperimental conditions studied without finding differences between treatments.CAT, APx and SOD activities were measured. Only SOD isozyme´s showed acontrasting response between accessions and treatments. NADPH and NADP+measurements results demonstrated that the first one was drastically reducedduring the stress treatment. Immunoblot of D1 and D2 PSII reaction centreprotein showed that D2 turnover was more evident than D1.As a conclusion, photoinhibitionoccurs in both ecotypes under cold stress, being MG-1 ecotype more sensiblethan MG-20. No drastic increased in ROS and RNS were observed in the conditionsstudied, however cell redox state seems to be affected. Alterations in D1 andD2 protein contents demonstrate that photodamage is occurring in our stressconditions. Our study may provide a deeper insight into the acclimationresponse of L. japonicus under coldstress.