PagMYB128 regulates secondary cell wall formation by direct activation of cell wall biosynthetic genes during wood formation in poplar.

The biosynthesis of cellulose, lignin, and hemicelluloses in plant secondary cell walls (SCWs) is regulated by a hierarchical transcriptional regulatory network. This network features orthologous transcription factors shared between poplar and Arabidopsis, highlighting a foundational similarity in their genetic regulation. However, knowledge on the discrepant behavior of the transcriptional-level molecular regulatory mechanisms between poplar and Arabidopsis remains limited. In this study, we investigated the function of PagMYB128 during wood formation and found it had broader impacts on SCW formation compared to its Arabidopsis ortholog, AtMYB103. Transgenic poplar trees overexpressing PagMYB128 exhibited significantly enhanced xylem development, with fiber cells and vessels displaying thicker walls, and an increase in the levels of cellulose, lignin, and hemicelluloses in the wood. In contrast, plants with dominant repression of PagMYB128 demonstrated the opposite phenotypes. RNA sequencing and reverse transcription - quantitative polymerase chain reaction showed that PagMYB128 could activate SCW biosynthetic gene expression, and chromatin immunoprecipitation along with yeast one-hybrid, and effector-reporter assays showed this regulation was direct. Further analysis revealed that PagSND1 (SECONDARY WALL-ASSOCIATED NAC-DOMAIN PROTEIN1) directly regulates PagMYB128 but not cell wall metabolic genes, highlighting the pivotal role of PagMYB128 in the SND1-driven regulatory network for wood development, thereby creating a feedforward loop in SCW biosynthesis.

The subgenomes show asymmetric expression of alleles in hybrid lineages of Megalobrama amblycephala × Culter alburnus.

Hybridization drives rapid speciation by shaping novel genotypic and phenotypic profiles. Genomic incompatibility and transcriptome shock have been observed in hybrids, although this is rarer in animals than in plants. Using the newly sequenced genomes of the blunt snout bream (Megalobrama amblycephala [BSB]) and the topmouth culter (Culter alburnus [TC]), we focused on the sequence variation and gene expression changes in the reciprocal intergeneric hybrid lineages (F1-F3) of BSB × TC. A genome-wide transcriptional analysis identified 145-974 expressed recombinant genes in the successive generations of hybrid fish, suggesting the rapid emergence of allelic variation following hybridization. Some gradual changes of gene expression with additive and dominance effects and various cis and trans regulations were observed from F1 to F3 in the two hybrid lineages. These asymmetric patterns of gene expression represent the alternative strategies for counteracting deleterious effects of the subgenomes and improving adaptability of novel hybrids. Furthermore, we identified positive selection and additive expression patterns in transforming growth factor, beta 1b (tgfb1b), which may account for the morphological variations of the pharyngeal jaw in the two hybrid lineages. Our current findings provide insights into the evolution of vertebrate genomes immediately following hybridization.

CAD1 and CCR2 protein complex formation in monolignol biosynthesis in Populus trichocarpa.

Lignin is the major phenolic polymer in plant secondary cell walls and is polymerized from monomeric subunits, the monolignols. Eleven enzyme families are implicated in monolignol biosynthesis. Here, we studied the functions of members of the cinnamyl alcohol dehydrogenase (CAD) and cinnamoyl-CoA reductase (CCR) families in wood formation in Populus trichocarpa, including the regulatory effects of their transcripts and protein activities on monolignol biosynthesis. Enzyme activity assays from stem-differentiating xylem (SDX) proteins showed that RNAi suppression of PtrCAD1 in P. trichocarpa transgenics caused a reduction in SDX CCR activity. RNAi suppression of PtrCCR2, the only CCR member highly expressed in SDX, caused a reciprocal reduction in SDX protein CAD activities. The enzyme assays of mixed and coexpressed recombinant proteins supported physical interactions between PtrCAD1 and PtrCCR2. Biomolecular fluorescence complementation and pull-down/co-immunoprecipitation experiments supported a hypothesis of PtrCAD1/PtrCCR2 heterodimer formation. These results provide evidence for the formation of PtrCAD1/PtrCCR2 protein complexes in monolignol biosynthesis in planta.

Comparing Modified with Conventional Parotidectomy for Benign Parotid Tumors.

PURPOSE: We conducted a study to compare the functional outcomes and surgical complications of patients with benign parotid tumors treated with conventional parotidectomy and modified parotidectomy. METHODS: This study retrospectively analyzed 99 patients who had benign parotid lesions and underwent parotidectomy using either conventional or modified parotidectomy. The operation time, cosmetic outcome, great auricular nerve anesthesia, incidence of Frey syndrome, and secretory function with the two techniques were compared. RESULTS: The mean operation time was shorter and the total complication rate was obviously lower in the modified surgery group (p < 0.001). In the modified surgery group, the incision was more cosmetic (p < 0.001), the sensory deficit rate was low (p < 0.001), and the sensory recovery rate was high, and transient facial paralysis and Frey syndrome were rare. Furthermore, glandular function was preserved in patients with a conserved Stensen duct. There was no tumor recurrence in the two groups during a mean follow-up of 29.8 months. CONCLUSION: Modified surgical techniques for benign parotid neoplasms significantly reduced the surgery time and improved the surgery outcomes compared with the conventional approach. This adds to the evidence to support the effectiveness of modified parotidectomy in selected patients with benign parotid tumors.

Decompression as a treatment for odontogenic cystic lesions of the jaw.

PURPOSE: To evaluate the effectiveness of decompression as the primary treatment of odontogenic cystic lesions of the jaw involving factors that affect relative shrinking speed and bone regeneration. PATIENTS AND METHODS: A total of 32 patients with odontogenic cystic lesions of the jaw underwent decompression with customized thermoplastic resin stents. Clinical examinations and pre- and postdecompression panoramic radiographs were analyzed. RESULTS: The mean relative speed of shrinkage of radicular cysts (RCs; 3.37 cm(2)/month) was faster than those of keratocystic odontogenic tumors (KCOTs; 2.87 cm(2)/month) and unicystic ameloblastomas (UABs; 2.71 cm(2)/month). The relative shrinking size increased linearly in a time-dependent manner for KCOTs (r = 0.849, P < .001), RCs (r = 0.681, P = .319), and UABs (r = 0.146, P = .730); a similar relation was detected between the primary radiolucent area of cystic lesions before decompression and relative shrinking speed after decompression in KCOTs (r = 0.481, P = .032), RCs (r = 0.260, P = .673), and UABs (r = 0.370, P = .366), but patient age did not affect the relative speed of shrinkage (P > .05). Furthermore, the increase in bone density was more significant in RCs than in KCOTs (P = .026) and UABs (P = .012) after decompression. CONCLUSION: Decompression was effective in reducing odontogenic cystic lesions of the jaw and increasing bone density. For aggressive lesions, secondary definitive surgery was necessary.

C2H2 zinc finger protein PagIDD15A regulates secondary wall thickening and lignin biosynthesis in poplar.

Wood production is largely determined by the activity of cambial cell proliferation, and the secondary cell wall (SCW) thickening of xylem cells determines the wood property. In this study, we identified an INDETERMINATE DOMAIN (IDD) type C2H2 zinc finger transcription factor PagIDD15A as a regulator of wood formation in Populus alba × Populus glandulosa. Downregulation of PagIDD15A expression by RNA interference (RNAi) inhibited xylem development and xylem cell secondary wall thickening. RNA-seq analysis showed that PagPAL1, PagCCR2 and PagCCoAOMT1 were downregulated in the differentiating xylem of the PagIDD15A-RNAi transgenic plants, showing that PagIDD15A may regulate SCW biosynthesis through inhibiting lignin biosynthesis. The downregulation of PagVND6-B2, PagMYB10 and PagMYC4 and upregulation of PagWRKY12 in the differentiating xylem of RNAi transgenic plants suggest that PagIDD15A may also regulate these transcription factor (TF) genes to affect SCW thickening. RT-qPCR analysis in the phloem-cambium of RNAi transgenic demonstrates that PagIDD15A may regulate the expression of the genes associated with cell proliferation, including, PagSHR (SHORTROOT), PagSCR (SCARECROW), PagCYCD3;1 (CYCLIN D3;1) and PagSMR4 (SIAMESE-RELATED4), to affect the cambial activity. This study provides the knowledge of the IDD-type C2H2 zinc finger protein in regulating wood formation.

Overexpression of a gibberellin 20-oxidase gene in poplar xylem led to an increase in the size of nanocellulose fibrils and improved paper properties.

Cellulose, the major component of secondary cell walls, is the most abundant renewable long-chain polymer on earth. Nanocellulose has become a prominent nano-reinforcement agent for polymer matrices in various industries. We report the generation of transgenic hybrid poplar overexpressing the Arabidopsis gibberellin 20-oxidase1 gene driven by a xylem-specific promoter to increase gibberellin (GA) biosynthesis in wood. X-ray diffraction (XRD) and sum frequency generation spectroscopic (SFG) analyses showed that cellulose in transgenic trees was less crystalline, but the crystal size was larger. The nanocellulose fibrils prepared from transgenic wood had an increased size compared to those from wild type. When such fibrils were used as a reinforcing agent in sheet paper preparation, the mechanical strength of the paper was significantly enhanced. Engineering the GA pathway can therefore affect nanocellulose properties, providing a new strategy for expanding nanocellulose applications.