CONICET | Buscador de Institutos y Recursos Humanos

Plenary Lecture Specific effects of solar UV-B radiation on plant defense mediated by the jasmonate signaling pathway Natural fluences of solar UV-B (c. 2 ìmol m-2 s-1, or 0.1 % of the total quantum flux between 285 and 700 nm) induce changes in plant secondary chemistry that have inordinately large effects on plant-insect interactions. The signal transduction pathways that mediate these highly specific effects of UV-B are not known. We investigated the role of jasmonates by measuring the responses to UV-B in wild-type (WT) and transgenic Nicotiana attenuata plants silenced in their lipoxygease gene to block jasmonate production (as-lox). In WT plants, UV-B failed to increase the levels of jasmonic acid (JA) or JA-Ile conjugates, but increased the response to wounding of jasmonate-inducible genes and promoted the accumulation of several phenylpropanoid derivatives. Some of the phenylpropanoid responses were missing in as-lox, whereas the effect of UV-B on accumulation of flavonoids was similar in both genotypes. As-lox plants were more susceptible to high UV-B than WT plants, suggesting that the phenylpropanoid derivatives that are not produced in these jasmonate-deficient plants are important for UV-B protection. In a herbivory trial under field conditions, as-lox plants supported more insect damage than WT plants, as expected. More importantly, the effects of UV-B increasing plant resistance to herbivory, which were highly significant in WT plants, were not detected in the as-lox line. We conclude: (1) some effects of natural UV-B fluxes on plant secondary chemistry require jasmonate biosynthesis; (2) these effects are likely mediated by changes in jasmonate sensitivity, and play a critical role in both UV-B protection and UV-B-induced anti-herbivore defense.