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.

Male sterility is a common phenomenon in the plant kingdom and based on the organelles harboring the male-sterility genes, it can be classified into the genic male sterility (GMS) and the cytoplasmic male sterility (CMS). In every generation, CMS can generate 100% male-sterile population, which is very important for the breeders to take advantage of the heterosis and for the seed producers to guarantee the seed purity. Celery is a cross-pollinated plant with the compound umbel type of inflorescence which carries hundreds of small flowers. These characteristics make CMS the only option to produce the commercial hybrid celery seeds. In this study, transcriptomic and proteomic analyses were performed to identify genes and proteins that are associated with celery CMS. A total of 1255 differentially expressed genes (DEGs) and 89 differentially expressed proteins (DEPs) were identified between the CMS and its maintainer line, then 25 genes were found to differentially expressed at both the transcript and protein levels. Ten DEGs involved in the fleece layer and outer pollen wall development were identified by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, most of which were down-regulated in the sterile line W99A. These DEGs and DEPs were mainly enriched in the pathways of “phenylpropanoid/sporopollenin synthesis/metabolism”, “energy metabolism”, “redox enzyme activity” and “redox processes”. Results obtained in this study laid a foundation for the future investigation of mechanisms of pollen development as well as the reasons for the CMS in celery.

Plant architecture is a major motif of plant diversity, and shoot branching patterns primarily determine the aerial architecture of plants. In this study, we identified an inbred pepper line with fewer lateral branches, 20C1734, which was free of lateral branches at the middle and upper nodes of the main stem with smooth and flat leaf axils. Successive leaf axil sections confirmed that in normal pepper plants, for either node n, P_n (Primordium n) < 1 cm and P_n+1 < 1 cm were the critical periods between the identification of axillary meristems and the establishment of the region, whereas P_n+3 < 1 cm was fully developed and formed a completely new organ. In 20C1734, the normal axillary meristematic tissue region establishment and meristematic cell identity confirmation could not be performed on the axils without axillary buds. Comparative transcriptome analysis revealed that “auxin-activated signaling pathway”, “response to auxin”, “response to abscisic acid”, “auxin biosynthetic process”, and the biosynthesis of the terms/pathways, such as “secondary metabolites”, were differentially enriched in different types of leaf axils at critical periods of axillary meristem development. The accuracy of RNA-seq was verified using RT-PCR for some genes in the pathway. Several differentially expressed genes (DEGs) related to endogenous phytohormones were targeted, including several genes of the PINs family. The endogenous hormone assay showed extremely high levels of IAA and ABA in leaf axils without axillary buds. ABA content in particular was unusually high. At the same time, there is no regular change in IAA level in this type of leaf axils (normal leaf axils will be accompanied by AM formation and IAA content will be low). Based on this, we speculated that the contents of endogenous hormones IAA and ABA in 20C1734 plant increased sharply, which led to the abnormal expression of genes in related pathways, which affected the formation of Ams in leaf axils in the middle and late vegetative growth period, and finally, nodes without axillary buds and side branches appeared.

The purple leaves of Brassica juncea are abundant in anthocyanins that confer stress tolerance, nutritional benefits, and ornamental value. In this study, we constructed F₂ and BC₁ segregating populations by crossing the purple leaf inbred line (ZY) with the green leaf inbred line (LY) to investigate the genetic basis of leaf pigmentation. Bulked segregant analysis sequencing (BSA-Seq) and map-based cloning localized the BjZY locus to a 162.08 kb interval on chromosome BB_Chr05. Based on sequence alignment and homology analysis, an R2R3 MYB transcription factor, BjMYB113 (BjuVB05G51160), was identified as a strong candidate gene, with 3 SNPs and 25 bp insert variants in the promoter region. The expression of BjMYB113 in purple leaves was significantly higher than that in green leaves, leading to anthocyanin biosynthesis and accumulation. The transient expression of BjMYB113 in tobacco leaf confirmed that BjMYB113 positively regulates anthocyanin biosynthesis. RNA-seq analysis revealed that BjMYB113 was involved in flavonoid and anthocyanin biosynthesis pathways and regulated the expression of anthocyanin-related genes, such as BjCHS, BjDFR, and BjANS. Yeast one-hybrid assays showed that BjMYB113 activated the expression of BjDFR by directly binding to its promoter. These results provide further understanding of the genetics of purple leaf and potential applications for marker-assisted breeding in B. juncea.