Beuchat J., Scacchi E., Tarkowska D., Ragni L., Strnad M., Hardtke Ch. S.
NEW PHYTOLOGIST
in press: DOI: 10.1111/j.1469-8137.2010.03387.x:
,
2010
Keywords:
Arabidopsis, auxin, brassinosteroid, BREVIS RADIX, shoot growth
Abstract:
BREVIS RADIX (BRX) has been identified through a loss-of-function allele in the
Umkirch-1 accession in a natural variation screen for Arabidopsis root growth
vigor. Physiological and gene expression analyses have suggested that BRX is rate
limiting for auxin-responsive gene expression by mediating cross-talk with the
brassinosteroid pathway, as impaired root growth and reduced auxin perception of
brx can be (partially) rescued by external brassinosteroid application.
• Using genetic tools, we show that brx mutants also display significantly reduced
cotyledon and leaf growth.
• Similar to the root, the amplitude and penetrance of this phenotype depends on
genetic background and shares the physiological features, reduced auxin
perception and brassinosteroid rescue. Furthermore, reciprocal grafting experiments
between mutant and complemented brx shoot scions and root stocks
suggest that the shoot phenotypes are not an indirect consequence of the root
phenotype. Finally, BRX gain-of-function lines display epinastic leaf growth and, in
the case of dominant negative interference, increased epidermal cell size.
Consistent with an impact of BRX on brassinosteroid biosynthesis, this phenotype
is accompanied by increased brassinosteroid levels.
• In summary, our results demonstrate a ubiquitous, although quantitatively variable
role of BRX in modulating the growth rate in both the root and shoot.
IEB authors: Miroslav Strnad,
Danuše Tarkowská
Čeština
English