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Blue‐light‐mediated shade avoidance requires combined auxin and brassinosteroid action in Arabidopsis seedlings
Author(s) -
Keuskamp Diederik H.,
Sasidharan Rashmi,
Vos Irene,
Peeters Anton J. M.,
Voesenek Laurentius A. C. J.,
Pierik Ronald
Publication year - 2011
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2011.04597.x
Subject(s) - shade avoidance , arabidopsis , auxin , brassinosteroid , phytochrome , hypocotyl , phototropism , photomorphogenesis , elongation , blue light , microbiology and biotechnology , arabidopsis thaliana , biology , botany , mutant , chemistry , biochemistry , red light , gene , physics , materials science , ultimate tensile strength , optics , metallurgy
Summary Plant growth in dense vegetation can be strongly affected by competition for light between neighbours. These neighbours can not only be detected through phytochrome‐mediated perception of a reduced red:far‐red ratio, but also through altered blue light fluence rates. A reduction in blue light (low blue) induces a set of phenotypic traits, such as shoot elongation, to consolidate light capture; these are called shade avoidance responses. Here we show that both auxin and brassinosteroids (BR) play an important role in the regulation of enhanced hypocotyl elongation of Arabidopsis seedlings in response to blue light depletion. Only when both hormones are experimentally blocked simultaneously, using mutants and chemical inhibitors, will the response be fully inhibited. Upon exposure to low blue several members of the cell wall modifying XYLOGLUCAN ENDOTRANSGLUCOSYLASE/HYDROLASE (XTH) protein family are regulated as well. Interestingly, auxin and BR each regulate a subset of these XTHs, by which they could regulate cell elongation. We hypothesize that auxin and BR regulate specific XTH genes in a non‐redundant and non‐synergistic manner during low‐blue‐induced shade avoidance responses of Arabidopsis seedlings, which explains why both hormones are required for an intact low‐blue response.