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Perennial trees have a recurring annual cycle of wood formation in response to environmental fluctuations. However, the precise molecular mechanisms that regulate the seasonal formation of wood remain poorly understood. Our prior study indicates that VCM1 and VCM2 play a vital role in regulating the activity of the vascular cambium by controlling the auxin homoeostasis of the cambium zone in Populus. This study indicates that abscisic acid (ABA) affects the expression of VCM1 and VCM2, which display seasonal fluctuations in relation to photoperiod changes. ABA‐responsive transcription factors AREB4 and AREB13, which are predominantly expressed in stem secondary vascular tissue, bind to VCM1 and VCM2 promoters to induce their expression. Seasonal changes in the photoperiod affect the ABA amount, which is linked to auxin‐regulated cambium activity via the functions of VCM1 and VCM2. Thus, the study reveals that AREB4/AREB13‐VCM1/VCM2‐PIN5b acts as a molecular module connecting ABA and auxin signals to control vascular cambium activity in seasonal wood formation. Summary statement: Perennial trees undergo a recurring annual process of wood formation in response to changes in the environment. This study demonstrates that the AREB4/AREB13‐VCM1/VCM2‐PIN5b module functions by linking abscisic acid and auxin signals to regulate the activity of the vascular cambium for the process of seasonal wood formation. [ABSTRACT FROM AUTHOR]

SUMMARY: The lenticel is a channel‐like structure that facilitates oxygen, carbon dioxide, and water vapor exchange on secondary growth tissue, such as a tree stem. Although the structure of lenticel has been described, there is limited understanding regarding the impact of this secondary structure on secondary growth as well as the cellular and metabolic processes underlying its formation. The study reveals the essential role of the lenticel in the process of tree secondary growth and the cellular and metabolic processes that take place during its formation. Under the stomata, lenticel development occurs when cells divide and differentiate into a structure of disconnected cells with air spaces between them. During lenticel formation, specific metabolic pathways and wax biosynthesis are activated. The SERK (somatic embryogenesis receptor kinase) gene controls lenticel density, and serk1serk3serk5 triple mutants enhance lenticel initiation. The findings shed light on the cellular and metabolic processes involved in lenticel formation, laying the groundwork for further mechanistic elucidation of their development, function, and genetic regulation in trees. Significance Statement: The lenticel is a porous, channel‐like structure that forms during plant secondary growth. Despite the description of the general structure of lenticels, their impact on plant growth and the specific cellular and molecular processes involved in their development remain incompletely understood. The study elucidates the critical role of the lenticel in tree growth and delineates the cellular process and metabolic specialization involved in its development. [ABSTRACT FROM AUTHOR]

Wood is an invaluable asset to human society due to its renewable nature, making it suitable for both sustainable energy production and material manufacturing. Additionally, wood derived from forest trees plays a crucial role in sequestering a significant portion of the carbon dioxide fixed during photosynthesis by terrestrial plants. Nevertheless, with the expansion of the global population and ongoing industrialization, forest coverage has been substantially decreased, resulting in significant challenges for wood production and supply. Wood production practices have changed away from natural forests toward plantation forests. Thus, understanding the underlying genetic mechanisms of wood formation is the foundation for developing high‐quality, fast‐growing plantation trees. Breeding ideal forest trees for wood production using genetic technologies has attracted the interest of many. Tremendous studies have been carried out in recent years on the molecular, genetic, and cell‐biological mechanisms of wood formation, and considerable progress and findings have been achieved. These studies and findings indicate enormous possibilities and prospects for tree improvement. This review will outline and assess the cellular and molecular mechanisms of wood formation, as well as studies on genetically improving forest trees, and address future development prospects. [ABSTRACT FROM AUTHOR]

Coordination of secondary cell wall deposition and cell expansion during plant growth is required for cell development, particularly in vascular tissues. Yet the fundamental coordination process has received little attention. We observed that the Arabidopsis endo-1,4-mannanase gene, AtMAN6 , is involved in the formation of cell walls in vascular tissues. In the inflorescence stem, the man6 mutant had smaller vessel cells with thicker secondary cell walls and shorter fiber cells. Elongation growth was reduced in the root, and secondary cell wall deposition in vessel cells occurred early. Overexpression of AtMAN6 resulted in the inverse phenotypes of the man6 mutant. AtMAN6 was discovered on the plasma membrane and was specifically expressed in vessel cells during its early development. The AtMAN6 protein degraded galactoglucomannan to produce oligosaccharides, which caused secondary cell wall deposition in vessel and fiber cells to be suppressed. Transcriptome analysis revealed that the expression of genes involved in the regulation of secondary cell wall synthesis was changed in both man6 mutant and AtMAN6 overexpression plants. AtMAN6's C-terminal cysteine repeat motif (CCRM) was found to facilitate homodimerization and is required for its activity. According to the findings, the oligosaccharides produced by AtMAN6 hydrolysis may act as a signal to mediate this coordination between cell growth and secondary cell wall deposition. [ABSTRACT FROM AUTHOR]

SUMMARY: Rosa roxburghii and Rosa sterilis, two species belonging to the Rosaceae family, are widespread in the southwest of China. These species have gained recognition for their remarkable abundance of ascorbate in their fresh fruits, making them an ideal vitamin C resource. In this study, we generated two high‐quality chromosome‐scale genome assemblies for R. roxburghii and R. sterilis, with genome sizes of 504 and 981.2 Mb, respectively. Notably, we present a haplotype‐resolved, chromosome‐scale assembly for diploid R. sterilis. Our results indicated that R. sterilis originated from the hybridization of R. roxburghii and R. longicuspis. Genome analysis revealed the absence of recent whole‐genome duplications in both species and identified a series of duplicated genes that possibly contributing to the accumulation of flavonoids. We identified two genes in the ascorbate synthesis pathway, GGP and GalLDH, that show signs of positive selection, along with high expression levels of GDP‐d‐mannose 3′, 5′‐epimerase (GME) and GDP‐l‐galactose phosphorylase (GGP) during fruit development. Furthermore, through co‐expression network analysis, we identified key hub genes (MYB5 and bZIP) that likely regulate genes in the ascorbate synthesis pathway, promoting ascorbate biosynthesis. Additionally, we observed the expansion of terpene synthase genes in these two species and tissue expression patterns, suggesting their involvement in terpenoid biosynthesis. Our research provides valuable insights into genome evolution and the molecular basis of the high concentration of ascorbate in these two Rosa species. [ABSTRACT FROM AUTHOR]

Lignin and cellulose are two essential elements of plant secondary cell walls that shape the mechanical characteristics of the culm to prevent lodging. However, how the regulation of the lignin and cellulose composition is combined to achieve optimal mechanical characteristics is unclear. Here, we show that increasing OsTCP19 expression in rice coordinately repressed lignin biosynthesis and promoted cellulose biosynthesis, resulting in enhanced lodging resistance. In contrast, repression of OsTCP19 coordinately promoted lignin biosynthesis and inhibited cellulose biosynthesis, leading to greater susceptibility to lodging. We found that OsTCP19 binds to the promoters of both MYB108 and MYB103L to increase their expression, with the former being responsible for repressing lignin biosynthesis and the latter for promoting cellulose biosynthesis. Moreover, up-regulation of OsTCP19 in fibers improved grain yield and lodging resistance. Thus, our results identify the OsTCP19-OsMYB108/OsMYB103L module as a key regulator of lignin and cellulose production in rice, and open up the possibility for precisely manipulating lignin–cellulose composition to improve culm mechanical properties for lodging resistance. [ABSTRACT FROM AUTHOR]

Summary: In trees, secondary xylem development is essential for the growth of perennial stem increments. Many signals regulate the process of development, but our knowledge of the molecular components involved in signal transduction is still limited.In this study, we identified Attenuation of Secondary Xylem (ASX) knockouts by screening genome‐editing knockouts of xylem‐expressed receptor‐like kinases (RLKs) in Populus. The ASX role in secondary xylem development in Populus was discovered using biochemical, cellular, and genomic analyses.The ASX knockout plants had abnormal secondary stem growth but had little effect on shoot apical primary growth. ASX and SOMATIC EMBRYOGENESIS RECEPTOR KINASE (SERK)2/4 were co‐precipitated in developing xylem. Through their interaction, ASX is phosphorylated by SERK. Transcriptome analysis of developing xylem revealed that ASX deficiency inhibited the transcriptional activity of genes involved in xylem differentiation and secondary cell wall formation. By forming a complex, ASX and SERK may function as a signaling module for signal transduction required in the regulation of secondary xylem development in trees.This study shows that ASX, which encodes a RLKs, is required for secondary xylem development and sheds light on regulatory signals found in tree stem secondary growth. [ABSTRACT FROM AUTHOR]

MYB transcriptional regulators belong to one of the most significant transcription factors families in plants, among which R2R3‐MYB transcription factors are involved in plant growth and development, hormone signal transduction, and stress response. Two R2R3‐MYB transcription factors, FLP and its paralogous AtMYB88, redundantly regulate the symmetrical division of guard mother cells (GMCs), and abiotic stress response in Arabidopsis thaliana. Only one orthologue gene of FLP was identified in pea (Pisum sativum FLP; PsFLP). In this study, we explored the gene function of PsFLP by virus‐induced gene silencing (VIGS) technology. The phenotypic analysis displayed that the silencing of PsFLP expression led to the abnormal development of stomata and the emergence of multiple guard cells tightly united. In addition, the abnormal stomata of flp could be fully rescued by PsFLP driven by the FLP promoter. In conclusion, the results showed that PsFLP plays a conservative negative role in regulating the symmetric division of GMC during stomatal development. Based on real‐time quantitative PCR, the relative expressions of AAO3, NCED3, and SnRK2.3 significantly increased in the flp pFLP::PsFLP plants compared to mutant, indicating that PsFLP might be involved in drought stress response. Thus, PsFLP regulates the genes related to cell cycle division during the stomatal development of peas and participates in response to drought stress. The study provides a basis for further research on its function and application in leguminous crop breeding. [ABSTRACT FROM AUTHOR]

SUMMARY: Vacuolar H+‐ATPase (V‐ATPase) has diverse functions related to plant development and growth. It creates the turgor pressure that drives cell growth by generating the energy needed for the active transport of solutes across the tonoplast. V‐ATPase is a large protein complex made up of multiheteromeric subunits, some of which have unknown functions. In this study, a forward genetics‐based strategy was employed to identify the vab3 mutant, which displayed resistance to isoxaben, a cellulose synthase inhibitor that could induce excessive transverse cell expansion. Map‐based cloning and genetic complementary assays demonstrated that V‐ATPase B subunit 3 (VAB3) is associated with the observed insensitivity of the mutant to isoxaben. Analysis of the vab3 mutant revealed defective ionic homeostasis and hypersensitivity to salt stress. Treatment with a V‐ATPase inhibitor exacerbated ionic tolerance and cell elongation defects in the vab3 mutant. Notably, exogenous low‐dose Ca2+ or Na+ could partially restore isoxaben resistance of the vab3 mutant, suggesting a relationship between VAB3‐regulated cell growth and ion homeostasis. Taken together, the results of this study suggest that the V‐ATPase subunit VAB3 is required for cell growth and ion homeostasis in Arabidopsis. Significance Statement: We identified a vab3 mutant. VAB3 is required for cell ion homeostasis and control of V‐ATPase‐related regulation of cell growth in Arabidopsis. [ABSTRACT FROM AUTHOR]