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Interaction of shade avoidance and auxin responses: a role for two novel atypical bHLH proteins
Author(s) -
RoigVillanova Irma,
BouTorrent Jordi,
Galstyan Anahit,
CarreteroPaulet Lorenzo,
Portolés Sergi,
RodríguezConcepción Manuel,
MartínezGarcía Jaime F
Publication year - 2007
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7601890
Subject(s) - biology
Plants sense the presence of potentially competing nearby individuals as a reduction in the red to far‐red ratio of the incoming light. In anticipation of eventual shading, a set of plant responses known as the s hade a voidance s yndrome (SAS) is initiated soon after detection of this signal by the phytochrome photoreceptors. Here we analyze the function of P HYTOCHROME R A PIDLY R EGULATED 1 ( PAR1) and PAR2 , two Arabidopsis thaliana genes rapidly upregulated after simulated shade perception. These genes encode two closely related atypical basic helix–loop–helix proteins with no previously assigned function in plant development. Using reverse genetic approaches, we show that PAR1 and PAR2 act in the nucleus to broadly control plant development, acting as negative regulators of a variety of SAS responses, including seedling elongation and photosynthetic pigment accumulation. Molecularly, PAR1 and PAR2 act as direct transcriptional repressors of two auxin‐responsive genes, S MALL A UXIN U P R EGULATED 15 ( SAUR15 ) and SAUR68 . Additional results support that PAR1 and PAR2 function in integrating shade and hormone transcriptional networks, rapidly connecting phytochrome‐sensed light changes with auxin responsiveness.