Auxin promotion of seedling growth via ARF5 is dependent on the brassinosteroid-regulated transcription factors BES1 and BEH4

Abstract

1Seedlings must continually calibrate their growth in response to the environment. Auxin and 2 brassinosteroids (BRs) are plant hormones that work together to control growth responses during 3 photomorphogenesis. We used our previous analysis of promoter architecture in an auxin and BR 4 target gene to guide our investigation into the broader molecular bases and biological relevance 5 of transcriptional co-regulation by these hormones. We found that the auxin-regulated 6 transcription factor AUXIN RESPONSIVE FACTOR 5 (ARF5) and the brassinosteroid-7 regulated transcription factor BRI1-EMS-SUPPRESOR 1/BRASSINOZOLERESISTANT 2 8 (BES1) co-regulated a subset of growth promoting genes via conserved bipartite cis-regulatory 9 elements. Moreover, ARF5 binding to DNA could be enriched by increasing BES1 levels. The 1 0 evolutionary loss of bipartite elements in promoters results in loss of hormone responsiveness. 1We also identified another member of the BES1/BZR1 family called BEH4 that acts partially 1 2 redundantly with BES1 to regulate seedling growth. Double mutant analysis showed that BEH4 1 3 and not BZR1 were required alongside BES1 for normal auxin response during early seedling 1 4 development. We propose that an ARF5-BES1/BEH4 transcriptional module acts to promote 1 5 growth via modulation of a diverse set of growth-associated genes. 1 6 1 7

Brassinosteroids Regulate Circadian Oscillation via the BES1/TPL-CCA1/LHY Module in Arabidopsis thaliana

“…The bri1-5 (Ws-2), bes1-D (En-2 background), bzr1-1D (Col-0 background), bes1-ko (Col-0 background), bzr1-2 (Col-0 background), pBES1::bes1-D-HA (Col-0 background), and pTPL-TPL-HA (Col-0 background) plants were previously described (Noguchi et al, 1999;Wang et al, 2002;Ryu et al, 2014;Galstyan and Nemhauser, 2019). The T-DNA insertion mutant tpl-8 (SALK_036566), bzr1-2 mutant (GK-857E04), and…”

Brassinosteroid transcription factor BES1 modulates nitrate deficiency by promoting NRT2.1 and NRT2.2 transcription in Arabidopsis

“…Low N promotes root elongation by enhancing BR signaling and improving the transport activity of auxin, which in turn is induced by BR (Devi et al, 2022). Both BR and auxin responses in plants mainly work through BES1 and BEH4 (Galstyan & Nemhauser, 2019). The nitrate-deficient phenotyping assay revealed that formation of both LRs and PRs of bes1-D were facilitated under low nitrate conditions (Figure 1b,c,e).…”

Genome-wide identification and characterization of the BES/BZR gene family in wheat and foxtail millet

“…Secondly, the master negative regulators of GA signaling, DELLAs (SLENDER-RICE1 [SLR1] in rice and GA IN-SENSITIVE [GAI], REPRESSOR OF GAI-3 [RGA], RGA-LIKE1 [RGL1], RGL2 and RGL3 in Arabidopsis), can inactivate the transcriptional regulatory activity of BZR1 and destabilize the BZR1 protein [14,15]. Thirdly, increased BES1 levels enhance DNA binding of auxin-regulated transcription factor AUXIN RESPONSIVE FACTOR 5 (ARF5) to its target promoters, and BES1/BZR1 HOMO-LOG 4 (BEH4), which is a paralog of BES1, acts in partial redundancy with BES1 for the normal auxin response during growth of Arabidopsis seedlings [16]. A fourth example of the crosstalk is that the transcription factor ZmBES1/BZR1-5 from maize (Zea mays L.) decreases sensitivity to ABA and positively regulates salt and drought tolerance in transgenic Arabidopsis [17].…”