Chunhua Wang

A compact plant architecture is a crucial agronomic trait that enhances crop yields by allowing for increased planting densities, thereby meeting the growing food requirements. We previously identified a GRAS family transcription factor, SCARECROW-LIKE28 (CsSCL28), from cucumber (Cucumis sativus L.) that regulates this process. However, the underlying regulatory mechanism remains unknown. Here, we demonstrated that CsSCL28 physically interacts with another GRAS family transcription factor SHORT-ROOT1 (CsSHR1). Knockout of CsSHR1 resulted in reduced plant height and leaf size. Overexpression of CsSHR1 regulates plant height and leaf size in cucumber in a dose-dependent manner. CsSHR1 positively regulates the transcription of CsSCL28. Genetic analyses revealed that CsSHR1 is epistatic to CsSCL28 in regulating cucumber plant architecture. Furthermore, CsSHR1 can directly activate the transcription of CsCYCD3;3, and ectopic overexpression of CYCD3;3 leads to an enlargement in leaf area. Biochemical data showed that CsSCL28 physically interacted with CsSHR1 to synergize its function by promoting the CsSHR1-mediated CsCYCD3;3 transcriptional activation. Importantly, appropriate overexpression of CsSHR1, which exhibits compact plant architecture, does not affect the yield per plant in cucumber. Thus, our findings reveal the genetic and molecular mechanism by which the CsSHR1 mediates compact plant architecture in cucumber. Our findings provide new gene targets for cucumber dense planting.

The ZF-HD transcription factors play key roles in plant development and stress responses, yet their functions in cucumber remain poorly understood. Here, we characterized a cucumber ZF-HD gene, CsHB33, and investigated its role in leaf development and drought tolerance. CsHB33 was highly expressed in developing leaves. Its expression was significantly suppressed by abscisic acid (ABA) and down-regulated under drought stress. Heterologous overexpression of CsHB33 in Arabidopsis promoted leaf growth by increasing cell size, but simultaneously enhanced sensitivity to osmotic and drought stress, accompanied by higher stomatal aperture and water loss. Transcriptomic analysis revealed that CsHB33 overexpression up-regulated genes associated with leaf enlargement, while under drought it led to constitutive activation of aromatic amino acid biosynthesis, particularly tryptophan metabolism. This metabolic disturbance likely contributes to the drought-sensitive phenotype. Our findings reveal that CsHB33 exerts opposing effects on leaf growth and drought tolerance, providing new insights into ZF-HD gene function in cucumber and identifying a potential target for improving stress resilience in breeding.

SUMMARY: Glandular trichomes (GTs) synthesize, store, and secrete diverse specialized metabolites that protect plants against biotic and abiotic stress. The bloom is deposited on the GTs and is perceptible on the surface of the cucumber fruit. Our previous investigation revealed the absence of bloom on the fruit surface in the loss‐of‐function CsMYB36 plants. GTs are formed through a series of cell differentiation events that support compound production. However, the mechanisms governing these events remain unclear. Here, we found GT cells initiate excessive periclinal divisions and fail to differentiate into functional GT cells in the absence of CsMYB36 based on the establishment of a detailed developmental process of GT in cucumber. We further found that CsMYB36 and CsGL1 form a positive feedback loop to regulate the cell differentiation of GT. DNA affinity purification (DAP)‐seq, combined with RNA‐seq data demonstrated that CsMYB36/CsGL1 can regulate the expression of phenylalanine synthesis‐related genes, including peroxidase 53 (CsPRX53) which is a reactive oxygen species (ROS)‐scavenging enzyme. H₂O₂ effectively inhibited GT cell division in Csmyb36 mutant plants. Collectively, our findings demonstrate that CsMYB36 combined with CsGL1 balances cell division and differentiation in the GT by mediating ROS homeostasis, thus affecting bloom production in cucumbers.

The hairy root induction system was used to efficiently investigate gene expression and function in plant root. Cucumber is a significant vegetable crop worldwide, with shallow roots, few lateral roots, and weak root systems, resulting in low nutrient absorption and utilization efficiency. Identifying essential genes related to root development and nutrient absorption is an effective way to improve the growth and development of cucumbers. However, genetic mechanisms underlying cucumber root development have not been explored. Here, we report a novel, rapid, effective hairy root transformation system. Compared to the in vitro cotyledon transformation method, this method shortened the time needed to obtain transgenic roots by 13 days. Furthermore, we combined this root transformation method with CRISPR/Cas9 technology and validated our system by exploring the expression and function of CsMYB36, a pivotal gene associated with root development and nutrient uptake. The hairy root transformation system established in this study provides a powerful method for rapidly identifying essential genes related to root development in cucumber and other horticultural crop species. This advancement holds promise for expediting research on root biology and molecular breeding strategies, contributing to the broader understanding and improvements crop growth and development.

The fruit neck is an important agronomic trait of cucumber (Cucumis sativus). However, the underlying genes and regulatory mechanisms involved in fruit neck development are poorly understood. We previously identified a cucumber yellow green peel (ygp) mutant, whose causal gene is MYB DOMAIN PROTEIN 36 (CsMYB36). This study showed that the ygp mutant exhibited a shortened fruit neck and repressed cell expansion in the fruit neck. Further functional analysis showed that CsMYB36 was also a target gene, and its expression was enriched in the fruit neck. Overexpression of CsMYB36 in the ygp mutant rescued shortened fruit necks. Furthermore, transcriptome analysis and reverse transcription quantitative polymerase chain reaction (RT-qPCR) assays revealed that CsMYB36 positively regulates the expression of an expansin-like A3 (CsEXLA3) in the fruit neck, which is essential for cell expansion. Yeast one-hybrid and dual-LUC assays revealed that CsMYB36 regulates fruit neck elongation by directly binding to the promoter of CsEXLA3. Collectively, these findings demonstrate that CsMYB36 is an important gene in the regulation of fruit neck length in cucumber plants.

Cucumber (Cucumis sativus L.) is an annual climbing herb that belongs to the Cucurbitaceae family and is one of the most important economic crops in the world. The breeding of cucumber varieties with excellent agronomic characteristics has gained more attention in recent years. The size and shape of the leaves or fruit and the plant architecture are important agronomic traits that influence crop management and productivity, thus determining the crop yields and consumer preferences. The growth of the plant is precisely regulated by both environmental stimuli and internal signals. Although significant progress has been made in understanding the plant morphological regulation of Arabidopsis, rice, and maize, our understanding of the control mechanisms of the growth and development of cucumber is still limited. This paper reviews the regulation of phytohormones in plant growth and expounds the latest progress in research regarding the genetic regulation pathways in leaf development, fruit size and shape, branching, and plant type in cucumber, so as to provide a theoretical basis for improving cucumber productivity and cultivation efficiency.

Cell wall lignification is a key step in forming functional endodermis and protoxylem (PX) in plant roots. Lignified casparian strips (CS) in endodermis and tracheary elements of PX are essential for selective absorption and transport of water and nutrients. Although multiple key regulators of CS and PX have been identified, the spatial information that drives the developmental shift to root lignification remains unknown. Here, we found that brassinosteroid (BR) signaling plays a key role in inhibiting root lignification in the root elongation zone. The inhibitory activity of BR signaling occurs partially through the direct binding of BRASSINAZOLE-RESISTANT 1 (BZR1) to SHORT-ROOT (SHR), repressing the SHR-mediated activation of downstream genes that are involved in root lignification. Upon entering the mature root zone, BR signaling declines rapidly, which releases SHR activity and initiates root lignification. Our results provide a mechanistic view of the developmental transition to cell wall lignification in Arabidopsis thaliana roots.

Vascular tissues are surrounded by an apoplastic barrier formed by endodermis that is vital for selective absorption of water and nutrients. Lignification and suberization of endodermal cell walls are fundamental processes in establishing the apoplastic barrier. Endodermal suberization in Arabidopsis (Arabidopsis thaliana) roots is presumed to be the integration of developmental regulation and stress responses. In root endodermis, the suberization level is enhanced when the Casparian strip, the lignified structure, is defective. However, it is not entirely clear how lignification and suberization interplay and how they interact with stress signaling. Here, in Arabidopsis, we constructed a hierarchical network mediated by SHORT-ROOT (SHR), a master regulator of endodermal development, and identified 13 key MYB transcription factors (TFs) that form multiple sub-networks. Combined with functional analyses, we further uncovered MYB TFs that mediate feedback or feed-forward loops, thus balancing lignification and suberization in Arabidopsis roots. In addition, sub-networks comprising nine MYB TFs were identified that interact with abscisic acid signaling to integrate stress response and root development. Our data provide insights into the mechanisms that enhance plant adaptation to changing environments.

The endoplasmic reticulum (ER) is a key compartment responsible for protein processing and folding, and it also participates in many signal transduction and metabolic processes. Reactive oxygen species (ROS) are important signaling messengers involved in the redox equilibrium and stress response. A number of abiotic and biotic stresses can trigger the accumulation of unfolded or misfolded proteins and lead to ER stress. In recent years, a number of studies have reported that redox metabolism and ROS are closely related to ER stress. ER stress can benefit ROS generation and even cause oxidative burden in plants, finally leading to oxidative stress depending on the degree of ER stress. Moreover, ER stress activates nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-mediated ROS signaling, increases antioxidant defense mechanisms, and alters the glutathione (GSH) redox state. Meanwhile, the accumulation of ROS plays a special role in inducing the ER stress response. Given these factors, plants have evolved a series of complex regulatory mechanisms to interact with ROS in response to ER stress. In this review, we summarize the perceptions and responses of plant ER stress and oxidative protein folding in the ER. In addition, we analyze the production and signaling of ROS under ER stress in detail in order to provide a theoretical basis for reducing ER stress to improve the crop survival rate in agricultural applications.