Down-regulation of Fra a 1.02 in strawberry fruits causes transcriptomic and metabolic changes compatible with an altered defense response

Multiple functions and regulatory networks of WRKY33 and its orthologs

Arabidopsis thaliana WRKY33 is currently one of the most studied members of the Group I WRKY transcription factor family. Research has confirmed that WRKY33 is involved in the regulation of various biological and abiotic stresses and occupies a central position in the regulatory network. The functional studies of orthologous genes of WRKY33 from other species are also receiving increasing attention. In this article, we summarized thirty-eight orthologous genes of AtWKRY33 from twenty-five different species. Their phylogenetic relationship and conserved WRKY domain were analyzed and compared. Similar to AtWKRY33, the well-studied orthologous gene members from rice and tomato also have multiple functions. In addition to playing important regulatory roles in responding to their specific pathogens, they are also involved in regulating various abiotic stresses and development. AtWKRY33 exerts its multiple functions through a complex regulatory network. Upstream transcription factors or other regulatory factors activate or inhibit the expression of AtWKRY33 at the chromatin and transcriptional levels. Interacting proteins affect the transcriptional activity of AtWKRY33 through phosphorylation, ubiquitination, SUMOylation, competition, or cooperation. The downstream genes are diverse and include three major categories: transcription factors, synthesis, metabolism, and signal transduction of various hormones, and disease resistance genes. In the regulatory network of AtWRKY33 orthologs, many conserved regulatory characteristics have been discovered, such as self-activation and phosphorylation by MAP kinases. This can provide a comparative reference for further studying the functions of other orthologous genes of AtWKRY33.

Microscale Thermophoresis Reveals Oxidized Glutathione as High-Affinity Ligand of Mal d 1

Pathogenesis-related (PR)-10 proteins, due to their particular secondary structure, can bind various ligands which could be important for their biological function. Accordingly, the PR-10 protein Mal d 1, the major apple allergen, probably also binds molecules in the hydrophobic cavity of its secondary structure, but it has not yet been investigated in this respect. In this study, various natural products found in apples such as flavonoids, glutathione (GSH), and glutathione disulfide (GSSG) were investigated as possible ligands of Mal d 1 using microscale thermophoresis. Dissociation constants of 16.39 µM, 29.51 µM, 35.79 µM, and 0.157 µM were determined for catechin, quercetin-3-O-rhamnoside, GSH, and GSSG, respectively. Molecular docking was performed to better understand the underlying binding mechanism and revealed hydrophobic interactions that stabilize the ligands within the pocket while hydrophilic interactions determine the binding of both GSH derivatives. The binding of these ligands could be important for the allergenicity of the PR-10 protein and provide further insights into its physiological role.

Elusive partners: a review of the auxiliary proteins guiding metabolic flux in flavonoid biosynthesis

Flavonoids are specialized metabolites widely distributed across the plant kingdom. They are involved in the growth and survival of plants, conferring the ability to filter ultra-violet rays, conduct symbiotic partnerships, and respond to stress. While many branches of flavonoid biosynthesis have been resolved, recent discoveries suggest missing auxiliary components. These overlooked elements can guide metabolic flux, enhance production, mediate stereoselectivity, transport intermediates, and exert regulatory functions. This review describes several families of auxiliary proteins from across the plant kingdom, including examples from specialized metabolism. In flavonoid biosynthesis, we discuss the example of chalcone isomerase-like (CHIL) proteins and their non-catalytic role. CHILs mediate the cyclization of tetraketides, forming the chalcone scaffold by interacting with chalcone synthase (CHS). Loss of CHIL activity leads to derailment of the CHS-catalyzed reaction and a loss of pigmentation in fruits and flowers. Similarly, members of the pathogenesis-related 10 (PR10) protein family have been found to differentially bind flavonoid intermediates, guiding the composition of anthocyanins. This role comes within a larger body of PR10 involvement in specialized metabolism, from outright catalysis (e.g., (S)-norcoclaurine synthesis) to controlling stereochemistry (e.g., enhancing cis-trans cyclization in catnip). Both CHILs and PR10s hail from larger families of ligand-binding proteins with a spectrum of activity, complicating the characterization of their enigmatic roles. Strategies for the discovery of auxiliary proteins are discussed, as well as mechanistic models for their function. Targeting such unanticipated components will be crucial in manipulating plants or engineering microbial systems for natural product synthesis.