Esthetic reconstruction of a localized severely resorbed anterior maxilla associated with peri-implantitis: A clinical report.

This clinical report described the esthetic reconstruction of a localized severely resorbed right anterior maxilla associated with peri-implantitis. For vertical bone augmentation, guided bone regeneration surgery was performed by raising a flap with the remote incision technique, followed by soft tissue grafting and vestibuloplasty. The biologically oriented preparation technique was used to improve the health and stability of the peri-implant tissues. The surgical treatment and a novel method of prosthetic rehabilitation provided excellent esthetic and functional outcomes.

TERMINAL FLOWER 1-FD complex target genes and competition with FLOWERING LOCUS T.

Plants monitor seasonal cues to optimize reproductive success by tuning onset of reproduction and inflorescence architecture. TERMINAL FLOWER 1 (TFL1) and FLOWERING LOCUS T (FT) and their orthologs antagonistically regulate these life history traits, yet their mechanism of action, antagonism and targets remain poorly understood. Here, we show that TFL1 is recruited to thousands of loci by the bZIP transcription factor FD. We identify the master regulator of floral fate, LEAFY (LFY) as a target under dual opposite regulation by TFL1 and FT and uncover a pivotal role of FT in promoting flower fate via LFY upregulation. We provide evidence that the antagonism between FT and TFL1 relies on competition for chromatin-bound FD at shared target loci. Direct TFL1-FD regulated target genes identify this complex as a hub for repressing both master regulators of reproductive development and endogenous signalling pathways. Our data provide mechanistic insight into how TFL1-FD sculpt inflorescence architecture, a trait important for reproductive success, plant architecture and yield.

A Direct Link between Abscisic Acid Sensing and the Chromatin-Remodeling ATPase BRAHMA via Core ABA Signaling Pathway Components.

Optimal response to drought is critical for plant survival and will affect biodiversity and crop performance during climate change. Mitotically heritable epigenetic or dynamic chromatin state changes have been implicated in the plant response to the drought stress hormone abscisic acid (ABA). The Arabidopsis SWI/SNF chromatin-remodeling ATPase BRAHMA (BRM) modulates response to ABA by preventing premature activation of stress response pathways during germination. We show that core ABA signaling pathway components physically interact with BRM and post-translationally modify BRM by phosphorylation/dephosphorylation. Genetic evidence suggests that BRM acts downstream of SnRK2.2/2.3 kinases, and biochemical studies identified phosphorylation sites in the C-terminal region of BRM at SnRK2 target sites that are evolutionarily conserved. Finally, the phosphomimetic BRM(S1760D S1762D) mutant displays ABA hypersensitivity. Prior studies showed that BRM resides at target loci in the ABA pathway in the presence and absence of the stimulus, but is only active in the absence of ABA. Our data suggest that SnRK2-dependent phosphorylation of BRM leads to its inhibition, and PP2CA-mediated dephosphorylation of BRM restores the ability of BRM to repress ABA response. These findings point to the presence of a rapid phosphorylation-based switch to control BRM activity; this property could be potentially harnessed to improve drought tolerance in plants.

AINTEGUMENTA and AINTEGUMENTA-LIKE6/PLETHORA3 Induce LEAFY Expression in Response to Auxin to Promote the Onset of Flower Formation in Arabidopsis.

Proper timing of the onset to flower formation is critical for reproductive success. Monocarpic plants like Arabidopsis (Arabidopsis thaliana) switch from production of branches in the axils of leaves to that of flowers once in their lifecycle, during the meristem identity transition. The plant-specific transcription factor LEAFY (LFY) is necessary and sufficient for this transition. Previously, we reported that the plant hormone auxin induces LFY expression through AUXIN RESPONSE FACTOR5/MONOPTEROS (ARF5/MP). It is not known whether MP is solely responsible for auxin-directed transcriptional activation of LFY. Here, we show that two transcription factors belonging to the AINTEGUMENTA-LIKE/PLETHORA family, AINTEGUMENTA (ANT) and AINTEGUMENTA-LIKE6/PLETHORA3 (AIL6/PLT3), act in parallel with MP to upregulate LFY in response to auxin. ant ail6 mutants display a delay in the meristem identity transition and in LFY induction. ANT and AIL6/PLT3 are expressed prior to LFY and bind to the LFY promoter to control LFY mRNA accumulation. Genetic and promoter/reporter studies suggest that ANT/AIL6 act in parallel with MP to promote LFY induction in response to auxin sensing. Our study highlights the importance of two separate auxin-controlled pathways in the meristem identity transition.

Control of Paternally Expressed Imprinted UPWARD CURLY LEAF1, a Gene Encoding an F-Box Protein That Regulates CURLY LEAF Polycomb Protein, in the Arabidopsis Endosperm.

Genomic imprinting, an epigenetic process in mammals and flowering plants, refers to the differential expression of alleles of the same genes in a parent-of-origin-specific manner. In Arabidopsis, imprinting occurs primarily in the endosperm, which nourishes the developing embryo. Recent high-throughput sequencing analyses revealed that more than 200 loci are imprinted in Arabidopsis; however, only a few of these imprinted genes and their imprinting mechanisms have been examined in detail. Whereas most imprinted loci characterized to date are maternally expressed imprinted genes (MEGs), PHERES1 (PHE1) and ADMETOS (ADM) are paternally expressed imprinted genes (PEGs). Here, we report that UPWARD CURLY LEAF1 (UCL1), a gene encoding an E3 ligase that degrades the CURLY LEAF (CLF) polycomb protein, is a PEG. After fertilization, paternally inherited UCL1 is expressed in the endosperm, but not in the embryo. The expression pattern of a ß-glucuronidase (GUS) reporter gene driven by the UCL1 promoter suggests that the imprinting control region (ICR) of UCL1 is adjacent to a transposable element in the UCL1 5'-upstream region. Polycomb Repressive Complex 2 (PRC2) silences the maternal UCL1 allele in the central cell prior to fertilization and in the endosperm after fertilization. The UCL1 imprinting pattern was not affected in paternal PRC2 mutants. We found unexpectedly that the maternal UCL1 allele is reactivated in the endosperm of Arabidopsis lines with mutations in cytosine DNA METHYLTRANSFERASE 1 (MET1) or the DNA glycosylase DEMETER (DME), which antagonistically regulate CpG methylation of DNA. By contrast, maternal UCL1 silencing was not altered in mutants with defects in non-CpG methylation. Thus, silencing of the maternal UCL1 allele is regulated by both MET1 and DME as well as by PRC2, suggesting that divergent mechanisms for the regulation of PEGs evolved in Arabidopsis.

Genetic evidence for the reduction of brassinosteroid levels by a BAHD acyltransferase-like protein in Arabidopsis.

Brassinosteroids (BRs) are a group of steroidal hormones involved in plant development. Although the BR biosynthesis pathways are well characterized, the BR inactivation process, which contributes to BR homeostasis, is less understood. Here, we show that a member of the BAHD (for benzylalcohol O-acetyltransferase, anthocyanin O-hydroxycinnamoyltransferase, anthranilate N-hydroxycinnamoyl/benzoyltransferase, and deacetylvindoline 4-O-acetyltransferase) acyltransferase family may play a role in BR homeostasis in Arabidopsis (Arabidopsis thaliana). We isolated two gain-of-function mutants, brassinosteroid inactivator1-1Dominant (bia1-1D) and bia1-2D, in which a novel BAHD acyltransferase-like protein was transcriptionally activated. Both mutants exhibited dwarfism, reduced male fertility, and deetiolation in darkness, which are typical phenotypes of plants defective in BR biosynthesis. Exogenous BR treatment rescued the phenotypes of the bia1-1D mutant. Endogenous levels of BRs were reduced in the bia1-1D mutant, demonstrating that BIA1 regulates endogenous BR levels. When grown in darkness, the bia1 loss-of-function mutant showed a longer hypocotyl phenotype and was more responsive to exogenous BR treatment than the wild-type plant. BIA1 expression was predominantly observed in the root, where low levels of BRs were detected. These results indicate that the BAHD acyltransferase family member encoded by BIA1 plays a role in controlling BR levels, particularly in the root and hypocotyl in darkness. Taken together, our study provides new insights into a mechanism that maintains BR homeostasis in Arabidopsis, likely via acyl conjugation of BRs.

An E3 ligase complex regulates SET-domain polycomb group protein activity in Arabidopsis thaliana.

Transcriptional repression via methylation of histone H3 lysine 27 (H3K27) by the polycomb repressive complex 2 (PRC2) is conserved in higher eukaryotes. The Arabidopsis PRC2 controls homeotic gene expression, flowering time, and gene imprinting. Although downstream target genes and the regulatory mechanism of PRC2 are well understood, much less is known about the significance of posttranslational regulation of PRC2 protein activity. Here, we show the posttranslational regulation of CURLY LEAF (CLF) SET-domain polycomb group (PcG) protein by the F-box protein, UPWARD CURLY LEAF1 (UCL1). Overexpression of UCL1 generates mutant phenotypes similar to those observed in plants with a loss-of-function mutation in the CLF gene. Leaf curling and early flowering phenotypes of UCL1 overexpression mutants, like clf mutants, are rescued by mutations in the AGAMOUS and FLOWERING LOCUS T genes, which is consistent with UCL1 and CLF functioning in the same genetic pathway. Overexpression of UCL1 reduces the level of CLF protein and alters expression and H3K27 methylation of CLF-target genes in transgenic plants, suggesting that UCL1 negatively regulates CLF. Interaction of UCL1 with CLF was detected in plant nuclei and in the yeast two-hybrid system. The UCL1 F-box binds in vivo to components of the E3 ligase complex, which ubiquitylate proteins that are subsequently degraded via the ubiquitin-26S proteasome pathway. Taken together, these results demonstrate the posttranslational regulation of the CLF SET-domain PcG activity by the UCL1 F-box protein in the E3 ligase complex.

Developmental and environmental regulation of soybean SE60 gene expression during embryogenesis and germination.

Soybean SE60 belongs to the gamma-thionin family of proteins. We recently demonstrated that SE60 plays a role in defense during soybean development. Here, we show that SE60 is expressed in a tissue-specific and developmentally regulated manner. The expression of SE60 is distinct from that of the glycinin (Gy2) and extensin (SbHRGP3) genes of soybean during embryogenesis and germination. A SE60::GUS(-809) transgene, comprising -809 bp of the 5'-flanking region of SE60 fused to the GUS reporter gene, was expressed specifically in developing embryos, but not in the endosperms, from the globular stage of transgenic tobacco and Arabidopsis seeds. Furthermore, light affected the SE60::GUS(-809) expression pattern in germinating seedlings. Electrophoretic mobility shift assay (EMSA) revealed that soybean nuclear proteins as well as E. coli-expressed SB16, a high mobility group protein (HMG), were bound sequence-specifically to the fragment containing AT-rich motifs identified in the SE60 promoter. Interestingly, the soybean nuclear proteins binding to the two G-boxes and RY repeat were prevalent in seeds of 2-4 mm in size. In contrast, the nuclear proteins binding to the AT-rich motif and SE60 RNA expression were more prominent in seeds of 4-6 mm in size. Therefore, we propose that factors binding to the G-boxes or RY repeat initiate SE60 expression during embryogenesis.