Genetic Interactions Between Brassinosteroid-Inactivating P450s and Photomorphogenic Photoreceptors in Arabidopsis thaliana

Abstract

Plants use light as a source of information via a suite of photomorphogenic photoreceptors to optimize growth in response to their light environment. Growth-promoting hormones such as brassinosteroids also can modulate many of these responses. BAS1 and SOB7 are brassinosteroid-catabolizing P450s in Arabidopsis thaliana that synergistically/redundantly modulate photomorphogenic traits such as flowering time. The role of BAS1 and SOB7 in photomorphogenesis has been investigated by studying null-mutant genetic interactions with the photoreceptors phyA, phyB, and cry1 with regard to seed germination and flowering time. The removal of BAS1 and/or SOB7 rescued the low germination rate of the phyA-211 phyB-9 double-null mutant. With regard to floral induction, bas1-2 and sob7-1 showed a complex set of genetic interactions with photoreceptor-null mutants. Histochemical analysis of transgenic plants harboring BAS1:BAS1-GUS and SOB7:SOB7-GUS translational fusions under the control of their endogenous promoters revealed overlapping and distinct expression patterns. BAS1’s expression in the shoot apex increases during the phase transition from short-to-long-day growth conditions and requires phyB in red light. In summary, BAS1 and SOB7 displayed both simple and complex genetic interactions with the phytochromes in a plant-stage specific manner.

ATAF2 integrates Arabidopsis brassinosteroid inactivation and seedling photomorphogenesis

“…The GUS expression patterns in pBAS1:BAS1-GUS/Col-0 and pSOB7:SOB7-GUS/Col-0 are similar, but not exactly identical to, those reported previously (Sandhu et al, 2012), which might also be a consequence of differences in T-DNA insertion position among ectopic expression lines. Additionally, differences in the genetic background might affect the GUS expression pattern observed.…”

“…Additionally, differences in the genetic background might affect the GUS expression pattern observed. Wild-type (Col-0) plants were used to generate GUS expression lines in this work, whereas Sandhu et al (2012) adopted a bas1-2 sob7-1 double-mutant background for pBAS1:BAS1-GUS and pSOB7:SOB7-GUS expression. …”

“…Similarly, GUS analysis showed that BAS1 and SOB7 have distinct, as well as overlapping, expression patterns and that these are limited to certain tissues, such as the shoot apex, root tip or root elongation zone (Sandhu et al, 2012). The interacted with pBAS1-EE (A), pBAS1-CBS1 (B) and pSOB7-CBS (C) in a targeted Y1H assay.…”

“…For the generation of ATAF2ox lines, the ATAF2 coding sequence was overexpressed in Col-0 under the control of the CaMV 35S promoter. The pBAS1:BAS1-GUS and pSOB7: SOB7-GUS constructs were described previously (Turk et al, 2003;Sandhu et al, 2012). Homozygous single-locus T-DNA insertion lines were selected for all three transgenic events.…”

“…Homozygous single-locus T-DNA insertion lines were selected for all three transgenic events. The histochemical GUS analysis was described previously (Sandhu et al, 2012). Photoreceptor mutants (all in the Col-0 background) phyB-9 (Reed et al, 1993), phyA-211 (Reed et al, 1994) and cry1-103 (Liscum and Hangarter, 1991) were crossed with ataf2-1 to isolate double mutants with ataf2-1 from F2 populations.…”