Cold and water stresses produce changes in endogenous jasmonates in two populations of Pinus pinaster Ait

There is considerable evidence suggesting that jasmonates (JAs) play a role in plant resistance against abiotic stress. It is well known that in Angiosperms JAs are involved in the defense response, however there is little information about their role in Gymnosperms. Our proposal was to study the involvement of JAs in Pinus pinaster Ait. reaction to cold and water stress, and to compare the response of two populations of different provenances (Gredos and Bajo Tiétar) to these stresses. We detected 12-oxo-phytodienoic acid (OPDA), jasmonic acid (JA), and the hydroxylates 11-hydroxyjasmonate and 12-hydroxyjasmonate in foliage and shoots of P. pinaster plants. The response of the Gredos population to cold stress differed from that of Bajo Tiétar. Gredos plants showed a lower JA-basal level than Bajo Tiétar; under cold stress JA increased twofold at 72 h, while it decreased in Bajo Tiétar plants. The hydroxylates slightly increased in both populations due to cold stress treatment. Under water stress, plants from Gredos showed a remarkable JA-increase; thus the JA-response was much more prominent under water stress than under cold stress. In contrast, no change was found in JA-level in Bajo Tiétar plants under water stress. The level of JA-precursor, OPDA, was very low in control plants from Gredos and Bajo Tiétar. Under water stress OPDA increased only in plants from Bajo Tiétar. Therefore, we inform here of a different JAs-accumulation pattern after the stress treatment in P. pinaster from two provenances, and suggest a possible correlation with adaptations to diverse ecological conditions.

Source: Plant Growth Regulation (2007) vol. 52, p.111-116

The Jasmonate-Induced Expression of the Nicotiana tabacum Leaf Lectin

Previous experiments with tobacco (Nicotiana tabacum L. cv Samsun NN) plants revealed that jasmonic acid methyl ester (JAME) induces the expression of a cytoplasmic/nuclear lectin in leaf cells and provided the first evidence that jasmonates affect the expression of carbohydrate-binding proteins in plant cells. To corroborate the induced accumulation of relatively large amounts of a cytoplasmic/nuclear lectin, a detailed study was performed on the induction of the lectin in both intact tobacco plants and excised leaves. Experiments with different stress factors demonstrated that the lectin is exclusively induced by exogeneously applied jasmonic acid and JAME, and to a lesser extent by insect herbivory. The lectin concentration depends on leaf age and the position of the tissue in the leaf. JAME acts systemically in intact plants but very locally in excised leaves. Kinetic analyses indicated that the lectin is synthesized within 12 h exposure time to JAME, reaching a maximum after 60 h. After removal of JAME, the lectin progressively disappears from the leaf tissue. The JAME-induced accumulation of an abundant nuclear/cytoplasmic lectin is discussed in view of the possible role of this lectin in the plant.

Source: Plant and cell physiology (2007) vol. 48, p. 1207-1218

Expression of an NADP-malic enzyme gene in rice (Oryza sativa. L) is induced by environmental stresses; over-expression of the gene in ...

Expression of an NADP-malic enzyme gene in rice (Oryza sativa. L) is induced by environmental stresses; over-expression of the gene in Arabidopsis confers salt and osmotic stress tolerance

NADP-malic enzyme (NADP-ME, EC 1.1.1.40) functions in many different pathways in plants, and has recently been implicated in plant defense such as in responses to wounding and UV-B radiation. In this study, we isolated a complementary DNA (cDNA) clone by using the differential display method and screening of a root cDNA library of rice (Oryza sativa. L) under carbonate (NaHCO3) stress, and identified it as one of the rice NADP-ME genes (we named it NADP-ME2, GenBank accession no. AB053295). The 5' end of NADP-ME2 was obtained by the 5'-RACE method, and the full-length cDNA had a length of 2217 bp encoding 593 amino acids. Expression of NADP-ME2 mRNA in roots was induced by stress from carbonates (NaHCO3 and Na2CO3, NaCl, and environmental pH changes. NADP-ME2 transcripts increased during 72-h exposures to NaHCO3, NaCl, and PEG stresses. Furthermore, NADP-ME activities in leaves and roots of rice seedlings increased by more than 50% in the presence of carbonates (NaHCO3 and Na2CO3), NaCl, and PEG. These results indicate that rice NADP-ME2 responds to salts and osmotic stresses. Transgenic Arabidopsis plants over-expressing NADP-ME2 were obtained through transformation, screening, Northern analysis and in situ NADP-ME activity assay. Transgenic Arabidopsis plants over-expressing NADP-ME2 grew well in 1/2 x MS medium with 100 mM NaCl or 4% mannitol, whereas growth of wild-type (WT) Arabidopsis seedlings was strongly inhibited. In addition, under 125 mM NaCl stress, the root lengths of transgenic lines were about twice as long as those of the WT. These results suggest that NADP-ME2 has a role in enhancing tolerance of plants to salt and osmotic stress.

Source: Plant Mol Biol. (2007) vol. 64, p. 49-58