Xu Li

Tree peony (Paeonia suffruticosa Andr.) is a traditional ornamental plant of high economic and cultural value, but its flower longevity is often limited by petal water loss. Cuticular wax serves as an essential barrier against non-stomatal water loss, and the AP2/EREBP (APETALA2/Ethylene-Responsive Element Binding Protein) transcription factor family is known to regulate wax biosynthesis. However, little information is available on the roles of AP2/EREBP genes in petal cuticle formation in tree peony. In this study, we performed transcriptome sequencing on petals of the tree peony cultivar ‘Bai Wang Shi Zi’ at three developmental stages (early, middle, and late). Using the assembled transcriptomic data, we identified 29 high-confidence AP2/EREBP family members, which were phylogenetically classified into AP2, ERF, and DREB subfamilies. Expression profiling revealed that 18 of these genes exhibited stage-specific expression patterns during petal development. Among them, two homologs of Arabidopsis SHN1 (SHINE 1) and WRI3 (WRINKLED 3), designated PsSHN1 and PsWRI3, showed peak expression at the middle stage. By co-expression analysis and phylogenetic comparison, three downstream candidate genes were identified and named PsCER2, PsKAS1, and PsLTPG1, based on their homology with known wax-related genes. Dual-luciferase reporter assays indicated that PsSHN1 and PsWRI3 can activate the promoters of PsCER2, PsKAS1, and PsLTPG1, suggesting a possible cooperative regulation of cuticle formation. Collectively, our findings provide promising candidate genes for prolonging floral lifespan by improving petal cuticular wax accumulation, and lay a preliminary foundation for molecular breeding and quality improvement of tree peony and other ornamental flowers.

Key message A mutation of CsARC6 not only causes white fruit color in cucumber, but also affects plant growth and fruit quality. Abstract Fruit color of cucumber is a very important agronomic trait, but most of the genes affecting cucumber white fruit color are still unknow, and no further studies were reported on the effect of cucumber fruit quality caused by white fruit color genes. Here, we obtained a white fruit mutant em41 in cucumber by EMS mutagenesis. The mutant gene was mapped to a 548 kb region of chromosome 2. Through mutation site analysis, it was found to be a null allele of CsARC6 (CsaV3_2G029290). The Csarc6 mutant has a typical phenotype of arc6 mutant that mesophyll cells contained only one or two giant chloroplasts. ARC6 protein was not detected in em41, and the level of FtsZ1 and FtsZ2 was also reduced. In addition, FtsZ2 could not form FtsZ ring-like structures in em41. Although these are typical arc6 mutant phenotypes, some special phenotypes occur in Csarc6 mutant, such as dwarfness with shortened internodes, enlarged fruit epidermal cells, decreased carotenoid contents, smaller fruits, and increased fruit nutrient contents. This study discovered a new gene, CsARC6, which not only controls the white fruit color, but also affects plant growth and fruit quality in cucumber.