MYB-bHLH-TTG1 in a Multi-tiered Pathway Regulates Arabidopsis Seed Coat Mucilage Biosynthesis Genes Including PECTIN METHYLESTERASE INHIBITOR14 Required for Homogalacturonan Demethylesterification.

MYB-bHLH-TTG1 (MBW) transcription factor (TF) complexes regulate Arabidopsis seed coat biosynthesis pathways via a multi-tiered regulatory mechanism. The MYB genes include MYB5, MYB23 and TRANSPARENT TESTA2 (TT2), which regulate GLABRA2 (GL2), HOMEODOMAIN GLABROUS2 (HDG2) and TRANSPARENT TESTA GLABRA2 (TTG2). Here, we examine the role of PECTIN METHYLESTERASE INHIBITOR14 (PMEI14) in seed coat mucilage pectin methylesterification and provide evidence in support of multi-tiered regulation of seed coat mucilage biosynthesis genes including PMEI14. The PMEI14 promoter was active in the seed coat and developing embryo. A pmei14 mutant exhibited stronger attachment of the outer layer of seed coat mucilage, increased mucilage homogalacturonan demethylesterification and reduced seed coat radial cell wall thickness, results consistent with decreased PMEI activity giving rise to increased PME activity. Reduced mucilage release from the seeds of myb5, myb23, tt2 and gl2, hdg2, ttg2 triple mutants indicated that HDG2 and MYB23 play minor roles in seed coat mucilage deposition. Chromatin immunoprecipitation analysis found that MYB5, TT8 and seven mucilage pathway structural genes are directly regulated by MYB5. Expression levels of GL2, HDG2, TTG2 and nine mucilage biosynthesis genes including PMEI14 in the combinatorial mutant seeds indicated that these genes are positively regulated by at least two of those six TFs and that TTG1 and TTG2 are major regulators of PMEI14 expression. Our results show that MYB-bHLH-TTG1 complexes regulate mucilage biosynthesis genes, including PMEI14, both directly and indirectly via a three-tiered mechanism involving GL2, HDG2 and TTG2.

MYB-bHLH-TTG1 Regulates Arabidopsis Seed Coat Biosynthesis Pathways Directly and Indirectly via Multiple Tiers of Transcription Factors.

MYB-bHLH-WDR (MBW) transcription factor (TF) complexes regulate Arabidopsis seed coat development including mucilage and tannin biosynthesis. The R2R3 MYBs MYB5, MYB23 and TRANSPARENT TESTA2 (TT2) participate in the MBW complexes with the WD-repeat protein TRANSPARENT TESTA GLABRA1 (TTG1). These complexes regulate GLABRA2 (GL2) and TTG2 expression in developing seeds. Microarray transcriptome analysis of ttg1-1- and wild-type (Ler) developing seeds identified 246 TTG1-regulated genes, which include all known metabolic genes of the tannin biosynthetic pathway. The first detailed TTG1-dependent metabolic pathways could be proposed for the biosynthesis of mucilage, jasmonic acid (JA) and cuticle including wax ester in developing seeds. We also assigned many known and previously uncharacterized genes to the activation/inactivation of hormones, plant immunity and nutrient transport. The promoters of six cuticle pathway genes were active in developing seeds. Expression of 11 genes was determined in the developing seeds of the combinatorial mutants of MYB5, MYB23 and TT2, and in the combinatorial mutants of GL2, HOMEODOMAIN GLABROUS2 (HDG2) and TTG2. These six TFs positively co-regulated the expression of four repressor genes while three of the six TFs repressed the wax biosynthesis genes examined, suggesting that the three TFs upregulate the expression of these repressor genes, which, in turn, repress the wax biosynthesis genes. Chromatin immunoprecipitation analysis identified 21 genes directly regulated by MYB5 including GL2, HDG2, TTG2, four repressor genes and various metabolic genes. We propose a multi-tiered regulatory mechanism by which MBWs regulate tannin, mucilage, JA and cuticle biosynthetic pathways.

Novel use of an adjustable single 8-0 polypropylene suture of scleral fixation without conjunctival dissection.

BACKGROUND: This report serves to describe the use of a novel adjustable single 8-0 polypropylene suture for scleral fixation without conjunctival dissection, and to describe related clinical outcomes associated with this approach. METHODS: In this study, we retrospectively reviewed 28 eyes from 27 patients that underwent scleral fixation of the intraocular lens (IOL) without conjunctival dissection using an adjustable single 8-0 polypropylene suture at the Beijing Tongren Eye Center between April 2018 and April 2019. For this surgical approach, a 23-gauge infusion cannula was set, after which two Hoffmann scleral pockets were created. Next, 8-0 polypropylene sutures were inserted into the eye guided by 10-0 polypropylene sutures of a long straight needle. The 8-0 suture was then used to fix the haptic IOs. Finally, these 8-0 polypropylene sutures were removed from the scleral pockets, and knots were tightened with the adjustable single suture. Primary outcomes included visual acuity and postoperative complication incidence. RESULTS: For this study, outcomes for 28 eyes from 27 patients (9 female, 18 male) were assessed. Patients had a mean age of 54 ± 15.11 years-old and were followed for an average of 10.18 ± 2.76 months postoperatively. Uncorrected visual acuity in these patients improved significantly from a preoperative value of 1.269 ± 0.464 logMAR to a 3-month postoperative value of 0.409 ± 0.413 logMAR (p = 0.000). The majority of postoperative complications in these patients were temporary and self-limiting, including corneal edema (35.71%), hypotony (14.29%), elevated intraocular pressure (28.58%), and mild hyphema (7.14%). No evidence of exposure or erosion of the trimmed suture end was detected in any patients. An ultrasound biomicroscope was able to readily detect the IOL and all sutures, and IOLs were found to be well-centered without any dislocation, tilting, or subluxation upon follow-up. CONCLUSIONS: An adjustable single 8-0 polypropylene suture can reliably and effectively be used for scleral fixation without conjunctival dissection for the treatment of patients with aphakia or inadequate posterior capsule support. The novel procedure described herein may therefore be an effective means of minimizing the risk of suture-related complications in patients undergoing scleral-fixated IOL implantation. TRIAL REGISTRATION: Retrospective case series study, not applicable. NCT04476264 .

A meta-analysis comparing the efficacy of mineralized collagen-polymethylmethacrylate and polymethylmethacrylate bone cements in the treatment of vertebral compression fractures.

PURPOSE: Vertebral compression fractures are often treated with vertebroplasty, and filling the injured vertebrae with bone cement is a key part of vertebroplasty. This meta-analysis was performed to compare the clinical efficacy and safety of mineralized collagen-polymethylmethacrylate (MC-PMMA) and polymethylmethacrylate (PMMA) bone cement in the treatment of vertebral compression fractures by vertebroplasty. METHODS: A computerized search of the published literature on mineralized collagen-polymethylmethacrylate and polymethylmethacrylate bone cement in the treatment of vertebral compression fractures was conducted in the China National Knowledge Infrastructure (CNKI), Wanfang database, PubMed, Embase, and Cochrane Library. The search was carried out from the time the database was created to March 2023 and 2 researchers independently conducted literature searches to retrieve a total of 884 studies, of which 12 were included in this meta-analysis. Cochrane systematic review methods were used to assess the quality of the literature and a meta-analysis was performed using ReviewManager 5.4 software. RESULTS: The results of the present meta-analysis showed that in postoperative adjacent vertebral fractures [OR = 0.25; 95% CI (0.15, 0.41)], postoperative cement leakage [OR = 0.45; 95% CI (0.30, 0.68)], Oswestry Disability Index (ODI) scores in the first 3 days after surgery [OR = -0.22; 95% CI (-0.42, -0.03)], ODI score at 6-12 months postoperatively [OR = -0.65; 95% CI (-0.97, -0.32)], visual analog scale (VAS) score at 6-12 months postoperatively [OR = -0.21; 95% CI (-0.46, 0.04)], and 1-year postoperative CT values [OR = 5.56; 95% CI (3.06, 8.06)], the MC-PMMA bone cement group was superior to the PMMA bone cement group. However, the differences between the two groups were not statistically different in terms of cement filling time, cement filling volume, operation time, intraoperative bleeding, hospitalization time, postoperative (<1 week, 3-6 months) vertebral body posterior convexity Cobb's angle, postoperative (<1 week, 6-12 months) vertebral body anterior margin relative height, postoperative (≤3 days, 1-3 months) pain VAS score and postoperative (1-3 months) ODI score. CONCLUSIONS: Compared with PMMA bone cement, the application of MC-PMMA bone cement is advantageous in reducing postoperative complications (adjacent vertebral fracture rate, cement leakage rate), pain relief, and functional recovery in the long-term postoperative period (>6 months), but there is still a need for more high-quality randomized controlled studies to provide more adequate evidence.