UV-B radiation, its effects and defense mechanisms in terrestrial plants

PRADO, FERNANDO; ROSA, MARIANA; PRADO, CAROLINA DEL VALLE; PODAZZA, GRISELDA; INTERDONATO, ROQUE; GONZÁLEZ, JUAN ANTONIO; HILAL, MIRNA

Environmental adaptations and stress tolerance of plants in the era of climate changes

Springer

Lugar: Nueva York; Año: 2011; p. 57 - 83

The UV-B is an important component of the solar radiation to which terrestrial and aquatic plants have been exposed during the early evolutionary history of the Earth. Hence, plants, principally terrestrial, have evolved different mechanisms to avoid and repair the UV-B damage; thereby, it is not surprising that photomorphogenic responses to solar UV-B are erroneously assumed to be adaptations to harmful radiation. Responses to UV-B enhancement include changes in the leaf area, leaf thickness, stomatal density, wax deposition, stem elongation and branching pattern, as well as in the synthesis of secondary metabolites, alterations in plant-pathogen and plant-predator interactions and gene expression. However, under field conditions the ambient solar UV-B provides an important signal for the normal plant development and may be perceived by plants through nondestructive processes that involve UV-B specific and UV-B nonspecific signaling pathways. Specific signaling pathways include the components UVR8 and COP1 which regulate the expression of a set of genes that are essential for the plant protection. Nonspecific signaling pathways involve the DNA damage, reactive oxygen species (ROS), hormones and wound/defense signaling molecules. Indeed under field conditions, the ambient UV-B might more properly be viewed as a photomorphogenic signal than as a stressor. Hence, it might not be appropriate evaluate the adaptive roles of plant responses to UV-B cues upon stress tolerance by the simultaneous application of both solar radiation and supplemental UV-B. In this chapter we analyzed the information regarding physiological and morphogenic responses of terrestrial plants to UV-B radiation, as well as the events related to UV-B perception, signal transduction, gene expression and ROS formation, from different studies carried out in greenhouses, growth chambers and field conditions.