Fruit peels of certain pepper (Capsicum annum L.) varieties accumulate a large amount of anthocyanins and exhibit purple color under medium-wave ultraviolet (UV-B) conditions, which severely impacts the commodity value of peppers. However, the regulatory mechanism of the above process has not been well studied so far. To explore which key genes are involved in this regulatory mechanism, pepper variety 19Q6100, the fruit peels of which turn purple under UV-B conditions, was investigated in this study. Transcription factors with expression levels significantly impacted by UV-B were identified by RNA-seq. Those genes may be involved in the regulation of UV-B-induced anthocyanin biosynthesis. Yeast one-hybrid results revealed that seven transcription factors, CabHLH143, CaMYB113, CabHLH137, CaMYBG, CaWRKY41, CaWRKY44 and CaWRKY53 directly bound to the putative promotor regions of the structural genes in the anthocyanin biosynthesis pathway. CaMYB113 was found to interact with CabHLH143 and CaHY5 by yeast two-hybrid assay, and those three genes may participate collaboratively in UV-B-induced anthocyanin biosynthesis in pepper fruit. Virus-induced gene silencing (VIGS) indicated that fruit peels of CaMYB113-silenced plants were unable to turn purple under UV-B conditions. These findings could deepen our understanding of UV-B-induced anthocyanin biosynthesis in pepper.

Celery (Apium graveolens L.) is an important leafy vegetable worldwide. The development of F₁ hybrids in celery is highly dependent on cytoplasmic male sterility (CMS) because emasculation is difficult. In this study, we first report a celery CMS, which was found in a high-generation inbred line population of the Chinese celery “tanzhixiangqin”. Comparative analysis, following sequencing and assembly of the complete mitochondrial genome sequences for this celery CMS line and its maintainer line, revealed that there are 21 unique regions in the celery CMS line and these unique regions contain 15 ORFs. Among these ORFs, only orf768a is a chimeric gene, consisting of 1497 bp sequences of the cox1 gene and 810 bp unidentified sequences located in the unique region, and the predicted protein product of orf768a possesses 11 transmembrane domains. In summary, the results of this study indicate that orf768a is likely to be a strong candidate gene for CMS induction in celery. In addition, orf768a can be a co-segregate marker, which can be used to screen CMS in celery.

Celery is one of the most popular vegetables in the world. The main edible parts of celery are the leaf blade and petiole. The celery petiole is usually green, red, or white, with a hollow or solid pith. However, the loci/genes controlling these petiole-related traits have not been reported. In this study, we present a chromosome-level celery genome assembly with a total size of 3.339 Gb. Simultaneous bursts of long-terminal repeats (78.43%) contributed greatly to the large genome size. Re-sequencing and population structure analysis of 79 celery accessions revealed that they could be divided into Chinese celery and Western celery. By combining genome-wide association studies (GWAS) and mapping data, we located the hollow petiole (hp) loci in an 807.6-kb region on chromosome 11. This study provides valuable resources for genetic research on celery and is also helpful for the identification and cloning of genes controlling leaf agronomic traits in celery.

Fruit ripening in non-climacteric species such as pepper (Capsicum annuum L.) is governed by a complex interplay of hormonal, transcriptional, and epigenetic factors. Here, we identified the NAC transcription factor CaNAC2 as an important regulator orchestrating pepper fruit ripening. CaNAC2 directly activated CaCCS, a key gene in capsanthin and capsorubin biosynthesis, and repressed CaCYP707A2, which encodes an ABA catabolic enzyme. Virus-induced gene silencing and overexpression assays confirmed that CaNAC2 promotes carotenoid accumulation and ABA biosynthesis, thereby accelerating ripening. Notably, CaNAC2 expression was activated by the ABA-responsive transcription factor CaABF3, forming a positive feedback loop (CaNAC2-CaCYP707A2-ABA-CaABF3) that sustained ABA accumulation in late ripening stages. Integrated DAP-seq and RNA-seq analyses revealed that CaNAC2 binds to and modulates the expression of multiple genes associated with carotenoid and ABA pathways. Moreover, DNA methylation levels at the promoters of CaNAC2, CaCYP707A2, and CaABF3 declined prior to ripening initiation, and 5-azacytidine treatment enhanced CaNAC2 expression and promoted ripening. While methylation-sensitive EMSAs suggested that cytosine methylation does not directly block transcription factor binding, elevated ABA levels suppressed DNA methyltransferase (CaCMT2) and induced demethylase (CaDML2) expression, reinforcing DNA hypomethylation. Together, these findings uncover CaNAC2 as a key integrator of hormonal and epigenetic signals and provide mechanistic insight into the coordinated transcriptional network driving pepper fruit ripening.