Reactive oxygen species (ROS) are unstable reactive molecules that are toxic to cells. Regulation of ROS homeostasis is crucial to protect cells from dysfunction, senescence, and death. In plant leaves, ROS are mainly generated from chloroplasts and are tightly temporally restricted by the circadian clock. However, little is known about how ROS homeostasis is regulated in nonphotosynthetic organs, such as petals. Here, we showed that hydrogen peroxide (H₂O₂) levels exhibit typical circadian rhythmicity in rose (Rosa hybrida) petals, consistent with the measured respiratory rate. RNA-seq and functional screening identified a B-box gene, RhBBX28, whose expression was associated with H₂O₂ rhythms. Silencing RhBBX28 accelerated flower senescence and promoted H₂O₂ accumulation at night in petals, while overexpression of RhBBX28 had the opposite effects. RhBBX28 influenced the expression of various genes related to respiratory metabolism, including the TCA cycle and glycolysis, and directly repressed the expression of SUCCINATE DEHYDROGENASE 1, which plays a central role in mitochondrial ROS (mtROS) homeostasis. We also found that PHYTOCHROME-INTERACTING FACTOR8 (RhPIF8) could activate RhBBX28 expression to control H₂O₂ levels in petals and thus flower senescence. Our results indicate that the circadian-controlled RhPIF8–RhBBX28 module is a critical player that controls flower senescence by governing mtROS homeostasis in rose.

The phytohormone auxin plays a pivotal role in floral meristem initiation and gynoecium development, but whether and how auxin controls floral organ identity remain largely unknown. Here, we found that auxin levels influence organ specification, and changes in auxin levels influence homeotic transformation between petals and stamens in rose (Rosa hybrida). The PIN-FORMED-LIKES (PILS) gene RhPILS1 governs auxin levels in floral buds during floral organogenesis. RhAUXIN RESPONSE FACTOR 18 (RhARF18), whose expression decreases with increasing auxin content, encodes a transcriptional repressor of the C-class gene RhAGAMOUS (RhAG), and controls stamen–petal organ specification in an auxin-dependent manner. Moreover, RhARF18 physically interacts with the histone deacetylase (HDA) RhHDA6. Silencing of RhHDA6 increases H3K9/K14 acetylation levels at the site adjacent to the RhARF18-binding site in the RhAG promoter and reduces petal number, indicating that RhARF18 might recruit RhHDA6 to the RhAG promoter to reinforce the repression of RhAG transcription. We propose a model for how auxin homeostasis controls floral organ identity via regulating transcription of RhAG

Anubias (Araceae) is a globally important group of ornamental aquatic plants. However, when temperatures drop to 10 °C, most species suffer obvious frostbite from cold stress, restricting winter cultivation and broader application. This study focused on two Anubias genotypes with distinct cold tolerance, adopting an integrated approach combining phenotypic, physiological, metabolomic, and transcriptomic analyses to reveal the mechanisms underlying their differential cold tolerance. Under 10 °C cold stress, compared with normal temperatures, the leaves of cold-tolerant Anubias sp. ‘Long Leaf’ (Jian) showed no significant frostbite, while cold-sensitive Anubias barteri var. nana ‘Coin Leaf’ (Jin) had clear frost damage. Both genotypes exhibited increased leaf relative electrical conductivity, malondialdehyde (MDA) content, soluble sugar content, and activities of superoxide dismutase (SOD) and catalase (CAT); “Jian” had more notable rises in SOD/CAT activities and maintained higher levels, whereas “Jin” showed greater increases in conductivity, MDA, and soluble sugar. Metabolomic and transcriptomic analyses revealed “Jian” specifically upregulated metabolites in pathways like flavone and flavonol biosynthesis and tryptophan metabolism, as well as genes related to valine, leucine, isoleucine degradation and phenylpropanoid biosynthesis pathways. ERFs, WRKYs, NACs and other transcription factors correlated with these differentially expressed genes, suggesting potential transcriptional regulation. These results provides insights for breeding cold-tolerant Anubias and optimizing low-temperature cultivation.

Stem diameter is an important agronomic trait determining plant architecture, lodging resistance and yield formation, yet its cytological and molecular mechanisms in the major cucurbit crop Luffa remain largely unclear. Herein, two Luffa inbred lines, S1174 (Luffa acutangula, thin stem) and P93075 (Luffa cylindrica, thick stem), were analyzed. Dynamic phenotyping uncovered a sigmoidal growth pattern with three key developmental stages: initiation (0 d), rapid growth (6 d), and maturation (20 d), during which P93075 consistently exhibited a significantly larger stem diameter than S1174 from 6 d onward. Anatomical analysis showed that P93075 displayed greater parenchyma cell size and vascular bundle area than S1174, suggesting that stem diameter variation is closely associated with parenchyma cell expansion and vascular bundle enlargement. Transcriptome profiling further identified 2611 differentially expressed genes (DEGs), mainly enriched in cell wall organization, phenylpropanoid biosynthesis, and hormone signaling pathways. Through temporal expression patterns of shared DEGs across developmental phases and co-expression network analysis, LacEXT3, encoding a cell wall extensin protein, was prioritized as a promising candidate gene associated with stem radial growth. Consistent with its markedly higher expression in P93075, heterologous overexpression of LacEXT3 in Arabidopsis resulted in increased stem diameter accompanied by reduced plant height. Overall, this study provides new insights into the developmental, cytological, and transcriptomic landscape underlying stem diameter variation in Luffa and offers a valuable resource for future investigation of the molecular mechanisms of stem thickening.