Characterization of the Molecular Events Underlying the Establishment of Axillary Meristem Region in Pepper.

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, Pn (Primordium n) < 1 cm and Pn+1 < 1 cm were the critical periods between the identification of axillary meristems and the establishment of the region, whereas Pn+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.

Transcriptomic and Proteomic Analyses of Celery Cytoplasmic Male Sterile Line and Its Maintainer Line.

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.

Loci underlying leaf agronomic traits identified by re-sequencing celery accessions based on an assembled genome.

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.

Different anthocyanin profiles of the skin and the pulp of Yan7 (Muscat Hamburg x Alicante Bouschet) grape berries.

Yan73 is a "teinturier" red wine variety cultivated in China and used in winemaking to strengthen red wine color. Here, the anthocyanin profile in both the skin and pulp of this grape variety was analyzed by HPLC-MS. The results showed that 18 anthocyanins were detected in both the skin and the pulp, and pelargonidin-3-O-glucoside, an anthocyanin compound hardly detected in most other Vitis viniferaberries, was found. However, the contents of individual anthocyanins in the skin and the pulp were significantly different. Compared with the skin, the pulp exhibited much lower ratio of 3',5'-substituted to 3'-substituted anthocyanins and much higher ratio of methoxylation of anthocyanin B-ring to non methoxylation, and with regard to the aromatic acylated and aliphatic acylated anthocyanins, both their contents in the skin are higher than in the pulp. The findings will provide some new insight for the tissue-specific expression and regulation of the genes involving in anthocyanin biosynthesis in grape berries.

Phenolic compound profiles in berry skins from nine red wine grape cultivars in northwest China.

Phenolic compound profiles were investigated by HPLC-MS in two consecutive years to assess genotypic variation in berry skins of nine red Vitis vinifera cultivars. The results showed that the types and levels of phenolic compounds greatly varied with cultivar. Common wine grape cultivars such as Syrah, Cabernet Sauvignon, Cabernet Gernischt and Merlot contained more types of anthocyanins, flavonols, flavan-3-ols, stilbenes and phenolic acids than Gamay, Yan73, Pinot Noir, Zinfandel and Muskat Rosovyi. Yan 73 and Pinot Noir had abundant anthocyanins, but only a few nonanthocyanin phenolic compounds. Gamay, Zinfandel and Muskat Rosovyi contained only a few anthocyanins and flavonols. For a grape cultivar, the ratio of one anthocyanin content to total anthocyanin content did not change greatly from one year to the next, unlike for non-anthocyanins. Cluster analysis showed that except for Syrah and Yan 73, the phenolic profiles in the tested grape cultivars had no significant year-to-year variations.