title: Antioxidant and photosystem II responses contribute to explain the drought-heat contrasting tolerance of two forage legumes.
abstract: Identification of metabolic targets of environmental stress factors is critical to improve the stress tolerance of plants. Studying the biochemical and physiological responses of plants with different capacities to deal with stress is a valid approach to reach this objective. Lotus corniculatus (lotus) and Trifolium pratense (clover) are legumes with contrasting summer stress tolerances. In stress conditions, which are defined as drought, heat or a combination of both, we found that differential biochemical responses of leaves explain these behaviours. Lotus and clover showed differences in water loss control, proline accumulation and antioxidant enzymatic capacity. Drought and/or heat stress induced a large accumulation of proline in the tolerant species (lotus), whereas heat stress did not cause proline accumulation in the sensitive species (clover). In lotus, Mn-SOD and Fe-SOD were induced by drought, but in clover, the SOD-isoform profile was not affected by stress. Moreover, lotus has more SOD-isoforms and a higher total SOD activity than clover. The functionality and electrophoretic profile of photosystem II (PSII) proteins under stress also exhibited differences between the two species. In lotus, PSII activity was drastically affected by combined stress and, interestingly, was correlated with D2 protein degradation. Possible implications of this event as an adaption mechanism in tolerant species are discussed. We conclude that the stress-tolerant capability of lotus is related to its ability to respond to oxidative damage and adaption of the photosynthetic machinery. This reveals that these two aspects should be included in the evaluation of the tolerance of species to stress conditions.
authors.affiliation: Laboratorio de Bioquímica, Departamento de Biología Vegetal, Facultad de Agronomía, Universidad de la República, Av. Garzón 780, CP 12900 Montevideo, Uruguay. ssignorelli@fagro.edu.uy
authors.forename: Santiago
authors.initials: S
authors.lastname: Signorelli
authors.forename: Esteban
authors.initials: E
authors.lastname: Casaretto
authors.forename: Martha
authors.initials: M
authors.lastname: Sainz
authors.forename: Pedro
authors.initials: P
authors.lastname: Díaz
authors.forename: Jorge
authors.initials: J
authors.lastname: Monza
authors.forename: Omar
authors.initials: O
authors.lastname: Borsani
mesh_terms: D000222:Adaptation, Physiological; D000975:Antioxidants; D055864:Droughts; D006358:Hot Temperature; D000070116:Lotus / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D010088:Oxidoreductases / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D011392:Proline / Q000378:metabolism; D013312:Stress, Physiological; D013482:Superoxide Dismutase / Q000378:metabolism; D029921:Trifolium / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D014867:Water
chemical_list: D000975:Antioxidants; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D014867:Water; D011392:Proline; D010088:Oxidoreductases; D013482:Superoxide Dismutase
keywords: APX; BSA; C; CAT; D; D + H; GR; H; H(2)O(2); HI; Heat stress; Lotus corniculatus; P5C; PSII; PSII proteins; Photoinhibition; Pro; Proline; ROS; SOD; Trifolium pratense; Water stress; ascorbate peroxidase; bovine seroalbumin; catalase; clover; control treatment; drought and heat treatment; drought treatment; glutathione reductase; heat treatment; hydric index; hydrogen peroxide; hydroxyl radicals; lotus; photosystem II; proline; pyrroline 5 carboxylate; reactive oxygen species; superoxide dismutase; superoxide radical