Abstract
Salinity stress represents a global constraint for rice, the most important staple food worldwide. Therefore the role of the central stress signal jasmonate for the salt response was analysed in rice comparing the responses to salt stress for two jasmonic acid (JA) biosynthesis rice mutants (cpm2 and hebiba) impaired in the function of ALLENE OXIDE CYCLASE (AOC) and their wild type. The aoc mutants were less sensitive to salt stress. Interestingly, both mutants accumulated smaller amounts of Na(+) ions in their leaves, and showed better scavenging of reactive oxygen species (ROS) under salt stress. Leaves of the wild type and JA mutants accumulated similar levels of abscisic acid (ABA) under stress conditions, and the levels of JA and its amino acid conjugate, JA-isoleucine (JA-Ile), showed only subtle alterations in the wild type. In contrast, the wild type responded to salt stress by strong induction of the JA precursor 12-oxophytodienoic acid (OPDA), which was not observed in the mutants. Transcript levels of representative salinity-induced genes were induced less in the JA mutants. The absence of 12-OPDA in the mutants correlated not only with a generally increased ROS-scavenging activity, but also with the higher activity of specific enzymes in the antioxidative pathway, such as glutathione S-transferase, and fewer symptoms of damage as, for example, indicated by lower levels of malondialdehyde. The data are interpreted in a model where the absence of OPDA enhanced the antioxidative power in mutant leaves.
Highlights
Soil salinization is a global threat that causes a huge reduction of agricultural yield worldwide
The role of the central stress signal jasmonate for the salt response was analysed in rice comparing the responses to salt stress for two jasmonic acid (JA) biosynthesis rice mutants impaired in the function of ALLENE OXIDE CYCLASE (AOC) and their wild type
It is noteworthy that mutants develop longer leaves due to deficiency in JA, which has been described for hebiba previously (Riemann et al, 2003)
Summary
Soil salinization is a global threat that causes a huge reduction of agricultural yield worldwide. Rice as a so-called glycophyte is very sensitive to salinity stress especially at the seedling stage, with height, root length, emergence of new roots, and dry matter affected significantly by salinity (Pearson et al, 1966; Akbar and Yabuno, 1974). Salinity stress is generally defined as the presence of excessive amounts of soluble salt that hinder or negatively affect the functions needed for normal plant growth and development. Salt stress is comprised of two harmful effects: osmotic stress leading to reduced water uptake, and ionic stress caused by the toxicity of specific ions (mainly Na+ and Cl–). Ionic stress leads to unrestrained overproduction of ROS (reactive oxygen species), such as superoxide radicals (O2·), hydrogen peroxide (H2O2), and hydroxyl
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