Yang Tian

Maca (Lepidium meyenii Walp, 2n = 8x = 64), belonging to the Brassicaceae family, is an economic plant cultivated in the central Andes sierra in Peru (4000-4500 m). Considering that the rapid uplift of the central Andes occurred 5-10 million years ago (Ma), an evolutionary question arises regarding how plants such as maca acquire high-altitude adaptation within a short geological period. Here, we report the high-quality genome assembly of maca, in which two closely spaced maca-specific whole-genome duplications (WGDs; ∼6.7 Ma) were identified. Comparative genomic analysis between maca and closely related Brassicaceae species revealed expansions of maca genes and gene families involved in abiotic stress response, hormone signaling pathway, and secondary metabolite biosynthesis via WGDs. The retention and subsequent functional divergence of many duplicated genes may account for the morphological and physiological changes (i.e., small leaf shape and self-fertility) in maca in a high-altitude environment. In addition, some duplicated maca genes were identified with functions in morphological adaptation (i.e., LEAF CURLING RESPONSIVENESS) and abiotic stress response (i.e., GLYCINE-RICH RNA-BINDING PROTEINS and DNA-DAMAGE-REPAIR/TOLERATION 2) under positive selection. Collectively, the maca genome provides useful information to understand the important roles of WGDs in the high-altitude adaptation of plants in the Andes.

The fish pathogen Vibrio alginolyticus contains two unique flagellar systems. The LuxS quorum sensing system is reported to regulate the expression of virulence factors in a wide variety of pathogenic bacteria. Our previous work demonstrated that inactive luxS led to decreased virulence in V. alginolyticus. In this study, LuxS-dependent regulation of motility and flagella biogenesis, the potential virulence factors in V. alginolyticus, were further investigated. A luxS-deleted mutant showed deficiency in motility and flagella formation, and an intact luxS complemented the defect. Since motility is flagella dependent, V. alginolyticus flagella biogenesis related genes, including the flagella regulator genes flaK and lafK and the sub-hierarchical flagellar genes fliS and lafA, were cloned and identified. Based on quantitative real-time reverse transcription-PCR, differential expression of these genes was confirmed in wild-type and luxS mutants. Our results indicate that LuxS plays an important role in the regulation of motility and flagella biogenesis in V. alginolyticus.

Egg yolk forms have several health and industrial applications, but their storage characteristics and gel mechanisms have not been thoroughly studied. In order to investigate the relationship between the changes in structure and properties of egg yolk gel and egg yolk powder during storage, in this paper, egg yolk powder was stored at 37 °C for 0, 1, 3, and 6 months in an accelerated storage experiment, and the influence of storage time on the gel properties of egg yolk powder was analyzed. The results showed that the contents of protein carbonylation and sulfhydryl in the yolk decreased gradually with the extension of storage time. Circular dichroism and fluorescence spectra showed that the ordered structure and structural stability of egg yolk proteins decreased gradually. Oxidation led to the formation of intermolecular crosslinking in the egg yolk proteins and oxidized aggregates, resulting in a decrease in surface hydrophobicity, which affected the gel properties of the egg yolk powder after rehydration, resulting in the phenomenon of lipid migration and gel degradation. The results provide a theoretical basis for improving egg yolk powder's overall quality and storage stability.