DELLA protein is a key negative regulator of gibberellin (GA) signaling. Although how DELLA regulates downstream gene expression remains unclear, DELLA has been proposed to function as a transcriptional activator. However, because DELLA lacks a DNAbinding domain, intermediate protein(s) mediating the DELLA/DNA interaction are believed to be necessary for activating DELLA target genes. Here, using yeast hybrid screenings, we identified five members of INDETERMINATE DOMAIN (IDD) protein family which bind physically to both DELLA and the promoter sequence of the GA-positive regulator SCARECROW-LIKE 3 (SCL3), which previously was characterized as a DELLA direct target gene. Transient assays using Arabidopsis protoplasts demonstrated that a luciferase reporter controlled by the SCL3 promoter was additively transactivated by REPRESSOR of ga1-3 (RGA) and IDDs. Phenotypic analysis of transgenic plants expressing AtIDD3 (one of the 16 IDDs in the Arabidopsis genome) fused with the plant-specific repression domain (SRDX) supported the possibility that AtIDD3 is positively involved in GA signaling. In addition, we found that SCL3 protein also interacts with IDDs, resulting in the suppression of its target gene expression. In this context, DELLA and SCL3 interact competitively with IDD proteins to regulate downstream gene expression. These results suggest that the coregulators DELLA and SCL3, using IDDs as transcriptional scaffolds for DNA binding, antagonistically regulate the expression of their downstream targets to control the GA signaling pathway.transcription factor | gibberellin feedback regulation | coactivator/corepressor exchange regulation system G ibberellins (GAs) are diterpene phytohormones that regulate many cellular and developmental events such as cell elongation, leaf expansion, flowering, pollen maturation, and the transition from vegetative growth to flowering (1-4). Several protein factors involved in GA signaling have been identified. Among these, DELLA protein is a key player in the regulation of GA responses. DELLA proteins are characterized by a DELLA/TVHYNP motif at the N terminus and a GRAS domain [named after its first three members: GA INSENSITIVE (GAI), REPRESSOR of ga1-3 (RGA), and SCARECROW (SCR)] at the C terminus, placing DELLAs within the GRAS family of transcriptional regulators. GRAS-domain transcription factors have diverse functions in growth and development. Recent intensive studies revealed how GA is perceived by the GA receptor GIBBERELLIN INSENSITIVE DWARF1 (GID1) and how the perceived GA signal is transmitted to DELLA. By binding to active GAs, GID1 acquires the ability to interact with DELLA, allowing further interaction with an F box protein, SLEEPY1/GID2. DELLA is polyubiquitinated by E3 ubiquitin-ligase SCF SLY1/GID2 and finally is degraded through the 26S proteasome. However, how DELLA regulates downstream gene expression in GA signaling has remained unclear.In Arabidopsis, five DELLA genes have been identified; GAI, RGA, and three RGA-LIKE proteins (RGL1, RGL2, and RGL3) (1-...

Although auxin and brassinosteroid (BR) synergistically control various plant responses, the molecular mechanism underlying the auxin-BR crosstalk is not well understood. We previously identified SMOS1, an auxin-regulated APETALA2-type transcription factor, as the causal gene of the small organ size 1 (smos1) mutant that is characterized by a decreased final size of various organs in rice. In this study, we identified another smos mutant, smos2, which shows the phenotype indistinguishable from smos1. SMOS2 was identical to the previously reported DWARF AND LOW-TILLERING (DLT), which encodes a GRAS protein involved in BR signaling. SMOS1 and SMOS2/DLT physically interact to cooperatively enhance transcriptional transactivation activity in yeast and in rice nuclei. Consistently, the expression of OsPHI-1, a direct target of SMOS1, is upregulated only when SMOS1 and SMOS2/DLT proteins are both present in rice cells. Taken together, our results suggest that SMOS1 and SMOS2/DLT form a keystone complex on auxin-BR signaling crosstalk in rice.

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Background. Pregnant women are a high-risk group for influenza-associated complications and hospitalizations.Methods. To examine the immunogenicity of a monovalent 2009 influenza A (H1N1) vaccine among pregnant women, a prospective cohort study was performed at 2 medical institutes of obstetrics in Japan. One hundred fifty subjects received 2 subcutaneous doses of vaccine 3 weeks apart. The hemagglutination inhibition antibody titer was measured in serum samples collected at 3 time points: before vaccination, 3 weeks after the first dose, and 4 weeks after the second dose.Results. The first dose of vaccine induced a ≥10-fold rise in the average level of antibody. The seroresponse rate (≥4-fold rise) was 91%, and the seroprotection rate (postvaccination titer ≥1:40) was 89%. The second dose of vaccine conferred little additional induction of antibodies. Similar immune responses were observed irrespective of body mass index before pregnancy, trimester, or age at vaccination. However, lesser immune response was shown in subjects who had received the 2009–2010 seasonal influenza vaccine before the H1N1 vaccination.Conclusions. A single dose of vaccine induced an adequately protective level of immunity in pregnant women. The potential interference with seasonal vaccination requires a more thorough investigation to prepare for future influenza pandemics.

SignificanceThe plant gibberellin receptor GID1 shows sequence similarity to carboxylesterase, suggesting that it is derived from an enzyme. However, how GID1 evolved and was modified is unclear. We identified two amino acids that are essential for GID1 activity, and we found that adjustment of these residues caused GID1 to recognize novel GAs carrying 13-OH as active GAs and to strictly refuse inactive GAs. Phylogenetic analysis of 169 GID1s revealed seven subtypes, and the B-type in core eudicots showed unique characteristics. In fact, certain B-type GID1s showed a higher nonsynonymous-to-synonymous divergence ratio in the region determining GA affinity. Such B-type GID1s with higher affinity were preferentially expressed in the roots in some core eudicot plants and conferred adaptive growth under stress.