RNA-Seq of Col-0 replicate 1 Total reads were mapped to the Arabidopsis thaliana genome (TAIR9, www.arabidopsis.org) using TopHat software. Read counts corresponding genes were generated using HTSeq with union mode.Genome Build:C_L1.count.txt: Arabidopsis TAIR9

Chromatin IP against PIF4 transcription factor Alignment : The raw sequence data were processed using Illumina sequence data analysis pipeline GAPipeline1.3.2. Sequences in Solexa FASTQ format were mapped to the Arabidopsis genome, TAIR9. Only unique mapping reads were used to determine PIF4 binding peaks.Peaks: Peak detection was performed with Plant Research International ChIP-seq Analysis Tool (PRI-CAT) (http://www.ab.wur.nl/pricat/)Genome Build:Col.aln: Arabidopsis genome (TAIR9)

RNA-Seq of pifq replicate 2 Total reads were mapped to the Arabidopsis thaliana genome (TAIR9, www.arabidopsis.org) using TopHat software. Read counts corresponding genes were generated using HTSeq with union mode.Genome Build:Q_L2.count.txt: Arabidopsis TAIR9

Chromatin IP against PIF4 transcription factor Alignment : The raw sequence data were processed using Illumina sequence data analysis pipeline GAPipeline1.3.2. Sequences in Solexa FASTQ format were mapped to the Arabidopsis genome, TAIR9. Only unique mapping reads were used to determine PIF4 binding peaks.Peaks: Peak detection was performed with Plant Research International ChIP-seq Analysis Tool (PRI-CAT) (http://www.ab.wur.nl/pricat/)Genome Build:PIF4.aln: Arabidopsis genome (TAIR9)PIF4_peaks.wig: Arabidopsis genome (TAIR9)

Environmental and endogenous signals, including light, temperature, brassinosteroid (BR), and gibberellin (GA), regulate cell elongation largely by influencing the expression of the paclobutrazol-resistant (PRE) family helix-loop-helix (HLH) factors, which promote cell elongation by interacting antagonistically with another HLH factor, IBH1. However, the molecular mechanism by which PREs and IBH1 regulate gene expression has remained unknown. Here, we show that IBH1 interacts with and inhibits a DNA binding basic helix-loop-helix (bHLH) protein, HBI1, in Arabidopsis thaliana. Overexpression of HBI1 increased hypocotyl and petiole elongation, whereas dominant inactivation of HBI1 and its homologs caused a dwarf phenotype, indicating that HBI1 is a positive regulator of cell elongation. In vitro and in vivo experiments showed that HBI1 directly bound to the promoters and activated two EXPANSIN genes encoding cell wall-loosening enzymes; HBI1's DNA binding and transcriptional activities were inhibited by IBH1, but the inhibitory effects of IBH1 were abolished by PRE1. The results indicate that PREs activate the DNA binding bHLH factor HBI1 by sequestering its inhibitor IBH1. Altering each of the three factors affected plant sensitivities to BR, GA, temperature, and light. Our study demonstrates that PREs, IBH1, and HBI1 form a chain of antagonistic switches that regulates cell elongation downstream of multiple external and endogenous signals.

Brassinosteroid (BR) regulates a wide range of physiological responses through the activation of BRASSINAZOLE RESISTANT1 (BZR1), whose activity is tightly controlled by its phosphorylation status and degradation. Although BZR1 appears to be degraded in distinct ways in response to different hormonal or environmental cues, little is known about how BR signaling regulates its degradation. Here we show that the BR-regulated U-box protein PUB40 mediates the proteasomal degradation of BZR1 in a root-specific manner in Arabidopsis (Arabidopsis thaliana). BZR1 levels were strongly reduced by plant U-box40 (PUB40) overexpression, whereas the pub39 pub40 pub41 mutant accumulated much more BZR1 than wild type in roots. The bzr1-1D gain-of-function mutation reduced the interaction with PUB40, which suppressed PUB40-mediated BZR1 degradation in roots. The cell layer-specific expression of PUB40 in roots helps induce selective BZR1 accumulation in the epidermal layer. Both BR treatment and loss-of-function of PUB40 expanded BZR1 accumulation to most cell layers. In addition, BZR1 accumulation increased the resistance of pub39 pub40 pub41 to low inorganic phosphate availability, as observed in bzrl-1D. BRASSINOSTEROID-INSENSITIVE2-induced phosphorylation of PUB40, which mainly occurs in roots, gives rise to BZR1 degradation through enhanced binding of PUB40 to BZR1 and PUB40's stability. Our results suggest a molecular mechanism of root-specific BZR1 degradation regulated by BR signaling.

Topological superconductivity with Majorana bound states, which are critical to implement nonabelian quantum computation, may be realized in three-dimensional semimetals with nontrivial topological feature, when superconducting transition occurs in the bulk. Here, we report pressure-induced superconductivity in a transition-metal dipnictide NbAs2. The emergence of superconductivity is not accompanied by any structural phase transition up to the maximum experimental pressure of 29.8 GPa, as supported by pressure-dependent synchrotron X-ray diffraction and Raman spectroscopy. Intriguingly, the Raman study reveals rapid phonon mode hardening and broadening above 10 GPa, in coincident with the superconducting transition. Using first-principle calculations, we determine Fermi surface change induced by pressure, which steadily increases the density of states without breaking the electron-hole compensation. Noticeably, the main hole pocket of NbAs2 encloses one time-reversal-invariant momenta of the monoclinic lattice, suggesting NbAs2 as a candidate of topological superconductors.

The receptor-like kinase SIT1 acts as a sensor in rice (Oryza sativa) roots, relaying salt stress signals via elevated kinase activity to enhance salt sensitivity. Here, we demonstrate that Protein Phosphatase 2A (PP2A) regulatory subunit B'kappa constrains SIT1 activity under salt stress. B'kappa-PP2A deactivates SIT1 directly by dephosphorylating the kinase at Thr515/516, a salt-induced phosphorylation site in the activation loop that is essential for SIT1 activity. B'kappa overexpression suppresses the salt sensitivity of rice plants expressing high levels of SIT1, thereby contributing to salt tolerance. B'kappa functions in a SIT1 kinase-dependent manner. During early salt stress, activated SIT1 phosphorylates B'kappa; this not only enhances its binding with SIT1, it also promotes B'kappa protein accumulation via Ser502 phosphorylation. Consequently, by blocking SIT1 phosphorylation, B'kappa inhibits and fine-tunes SIT1 activity to balance plant growth and stress adaptation.

The receptor-like kinase SIT1 acts as a sensor in rice (Oryza sativa) roots, relaying salt stress signals via elevated kinase activity to enhance salt sensitivity. Here, we demonstrate that Protein Phosphatase 2A (PP2A) regulatory subunit B'kappa constrains SIT1 activity under salt stress. B'kappa-PP2A deactivates SIT1 directly by dephosphorylating the kinase at Thr515/516, a salt-induced phosphorylation site in the activation loop that is essential for SIT1 activity. B'kappa overexpression suppresses the salt sensitivity of rice plants expressing high levels of SIT1, thereby contributing to salt tolerance. B'kappa functions in a SIT1 kinase-dependent manner. During early salt stress, activated SIT1 phosphorylates B'kappa; this not only enhances its binding with SIT1, it also promotes B'kappa protein accumulation via Ser502 phosphorylation. Consequently, by blocking SIT1 phosphorylation, B'kappa inhibits and fine-tunes SIT1 activity to balance plant growth and stress adaptation.

The American biologist Winslow Russel Briggs (1928-2019) was a global leader in plant physiology, genetics and photobiology. In this contribution, we try to share our knowledge of the remarkable career of this outstanding scientist. After earning his PhD at Harvard (Cambridge, Massachusetts), he started his independent research program at Stanford University (California). Among many major contributions was his elegant experiment that conclusively demonstrated the role of auxin transport in the phototropic bending response of grass coleoptiles. During subsequent years as Professor of biology at Harvard University, Briggs focused on phytochrome and photomorphogenesis. In 1973, he re-located to Stanford to become Director of the Department of Plant Biology, Carnegie Institution for Science, and faculty member in the Biology Department at Stanford University. After his retirement (1993), he continued his research on "light and plant development" as an emeritus at Carnegie until the day of his death on February 11, 2019. Through his long research career, Briggs stayed at the cutting edge by re-inventing himself from a plant physiologist, to biochemist, geneticist, and molecular biologist. He made numerous discoveries, including the LOV-domain photoreceptor phototropin. Winslow Briggs, who was also a naturalist and gifted pianist, inspired and promoted the work of generations of young scientists - as mentor, colleague and friend.