27 / 10 / 2009

Abscisic acid is involved in the response of grape (Vitis vinifera L.) cv. Malbec leaf tissues to ultraviolet-B radiation by enhancing ultraviolet-absorbing compounds, antioxidant enzymes and membrane sterols.

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Por: Federico J. BERLI, Daniela MORENO, Patricia PICCOLI, Leandro HESPANHOL-VIANA, M. Fernanda SILVA, Ricardo BRESSAN-SMITH, J. Bruno CAVAGNARO, Rubén BOTTINI. En: Plant, Cell and Environment (2009)

We investigated the interactions of abscisic acid (ABA) in the responses of grape leaf tissues to contrasting ultraviolet (UV)-B treatments. One-year-old field-grown plants of
Vitis vinifera L. were exposed to photosynthetically active radiation (PAR) where solar UV-B was eliminated by using polyester filters, or where PAR was supplemented
with UV-B irradiation. Treatments combinations included weekly foliar sprays of ABA or a water control. The levels of UV-B absorbing flavonols, quercetin and kaempferol
were significantly decreased by filtering out UV-B, while appliedABA increased their content. Concentration of two hydroxycinnamic acids, caffeic and ferulic acids, were also
increased by ABA, but not affected by plus UV-B (+UV-B) treatments. Levels of carotenoids and activities of the antioxidant enzymes, catalase, ascorbate peroxidase and
peroxidase were elevated by +ABA treatments, but only if +UV-B was given. Cell membrane b-sitosterol was enhanced by ABA independently of +UV-B. Changes in
photoprotective compounds, antioxidant enzymatic activities and sterols were correlated with lessened membrane harm by UV-B, as assessed by ion leakage. Oxidative
damage expressed as malondialdehyde content was increased under +UV-B treatments.Our results suggest that the defence system of grape leaf tissues against UV-B is activated by UV-B irradiation with ABA acting downstream in the signalling pathway.

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