title: Jasmonate-dependent and -independent pathways mediate specific effects of solar ultraviolet B radiation on leaf phenolics and antiherbivore defense.
abstract: Ultraviolet B (UV-B) radiation, a very small fraction of the daylight spectrum, elicits changes in plant secondary metabolism that have large effects on plant-insect interactions. The signal transduction pathways that mediate these specific effects of solar UV-B are not known. We examined the role of jasmonate signaling by measuring responses to UV-B in wild-type and transgenic jasmonate-deficient Nicotiana attenuata plants in which a lipoxygenase gene (NaLOX3) was silenced (as-lox). In wild-type plants, UV-B failed to elicit the accumulation of jasmonic acid (JA) or the bioactive JA-isoleucine conjugate but amplified the response of jasmonate-inducible genes, such as trypsin proteinase inhibitor (TPI), to wounding and methyl jasmonate, and increased the accumulation of several phenylpropanoid derivatives. Some of these phenolic responses (accumulation of caffeoyl-polyamine conjugates) were completely lacking in as-lox plants, whereas others (accumulation of rutin and chlorogenic acid) were similar in both genotypes. In open field conditions, as-lox plants received more insect damage than wild-type plants, as expected, but the dramatic increase in resistance to herbivory elicited by UV-B exposure, which was highly significant in wild-type plants, did not occur in as-lox plants. We conclude that solar UV-B (1) uses jasmonate-dependent and -independent pathways in the elicitation of phenolic compounds, and (2) increases sensitivity to jasmonates, leading to enhanced expression of wound-response genes (TPI). The lack of UV-B-induced antiherbivore protection in as-lox plants suggests that jasmonate signaling plays a central role in the mechanisms by which solar UV-B increases resistance to insect herbivores in the field.
authors.affiliation: Instituto de Investigaciones Fisiológicas y Ecológicas vinculadas a Agricultura, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad de Buenos Aires, C1417DSE Buenos Aires, Argentina.
authors.forename: Patricia V
authors.initials: PV
authors.lastname: Demkura
authors.forename: Guillermina
authors.initials: G
authors.lastname: Abdala
authors.forename: Ian T
authors.initials: IT
authors.lastname: Baldwin
authors.forename: Carlos L
authors.initials: CL
authors.lastname: Ballaré
mesh_terms: D000085:Acetates / Q000494:pharmacology; D000818:Animals; D003517:Cyclopentanes / Q000378:metabolism* / Q000494:pharmacology; D020868:Gene Silencing; D007313:Insecta; D054883:Oxylipins / Q000378:metabolism* / Q000494:pharmacology; D010636:Phenols / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D015398:Signal Transduction; D013472:Sunlight; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D000085:Acetates; D003517:Cyclopentanes; D054883:Oxylipins; D010636:Phenols; C011006:jasmonic acid; C072239:methyl jasmonate