Control of meiotic crossover interference by a proteolytic chaperone network.

Meiosis is a specialized eukaryotic division that produces genetically diverse gametes for sexual reproduction. During meiosis, homologous chromosomes pair and undergo reciprocal exchanges, called crossovers, which recombine genetic variation. Meiotic crossovers are stringently controlled with at least one obligate exchange forming per chromosome pair, while closely spaced crossovers are inhibited by interference. In Arabidopsis, crossover positions can be explained by a diffusion-mediated coarsening model, in which large, approximately evenly spaced foci of the pro-crossover E3 ligase HEI10 grow at the expense of smaller, closely spaced clusters. However, the mechanisms that control HEI10 dynamics during meiosis remain unclear. Here, through a forward genetic screen in Arabidopsis, we identified high crossover rate3 (hcr3), a dominant-negative mutant that reduces crossover interference and increases crossovers genome-wide. HCR3 encodes J3, a co-chaperone related to HSP40, which acts to target protein aggregates and biomolecular condensates to the disassembly chaperone HSP70, thereby promoting proteasomal degradation. Consistently, we show that a network of HCR3 and HSP70 chaperones facilitates proteolysis of HEI10, thereby regulating interference and the recombination landscape. These results reveal a new role for the HSP40/J3-HSP70 chaperones in regulating chromosome-wide dynamics of recombination via control of HEI10 proteolysis.

Arabidopsis HEAT SHOCK FACTOR BINDING PROTEIN is required to limit meiotic crossovers and HEI10 transcription.

The number of meiotic crossovers is tightly controlled and most depend on pro-crossover ZMM proteins, such as the E3 ligase HEI10. Despite the importance of HEI10 dosage for crossover formation, how HEI10 transcription is controlled remains unexplored. In a forward genetic screen using a fluorescent crossover reporter in Arabidopsis thaliana, we identify heat shock factor binding protein (HSBP) as a repressor of HEI10 transcription and crossover numbers. Using genome-wide crossover mapping and cytogenetics, we show that hsbp mutations or meiotic HSBP knockdowns increase ZMM-dependent crossovers toward the telomeres, mirroring the effects of HEI10 overexpression. Through RNA sequencing, DNA methylome, and chromatin immunoprecipitation analysis, we reveal that HSBP is required to repress HEI10 transcription by binding with heat shock factors (HSFs) at the HEI10 promoter and maintaining DNA methylation over the HEI10 5' untranslated region. Our findings provide insights into how the temperature response regulator HSBP restricts meiotic HEI10 transcription and crossover number by attenuating HSF activity.

Long-term abscisic acid promotes golden2-like1 degradation through constitutive photomorphogenic 1 in a light intensity-dependent manner to suppress chloroplast development.

Abiotic stress, a serious threat to plants, occurs for extended periods in nature. Abscisic acid (ABA) plays a critical role in abiotic stress responses in plants. Therefore, stress responses mediated by ABA have been studied extensively, especially in short-term responses. However, long-term stress responses mediated by ABA remain largely unknown. To elucidate the mechanism by which plants respond to prolonged abiotic stress, we used long-term ABA treatment that activates the signalling against abiotic stress such as dehydration and investigated mechanisms underlying the responses. Long-term ABA treatment activates constitutive photomorphogenic 1 (COP1). Active COP1 mediates the ubiquitination of golden2-like1 (GLK1) for degradation, contributing to lowering expression of photosynthesis-associated genes such as glutamyl-tRNA reductase (HEMA1) and protochlorophyllide oxidoreductase A (PORA), resulting in the suppression of chloroplast development. Moreover, COP1 activation and GLK1 degradation upon long-term ABA treatment depend on light intensity. Additionally, plants with COP1 mutation or exposed to higher light intensity were more sensitive to salt stress. Collectively, our results demonstrate that long-term treatment of ABA leads to activation of COP1 in a light intensity-dependent manner for GLK1 degradation to suppress chloroplast development, which we propose to constitute a mechanism of balancing normal growth and stress responses upon the long-term abiotic stress.

Production of bacteriophage-encoded endolysin, LysP11, in Nicotiana benthamiana and its activity as a potent antimicrobial agent against Erysipelothrix rhusiopathiae.

KEY MESSAGE: We produced a biologically active phage-encoded endolysin, LysP11, in N. benthamiana. Plant-produced LysP11 exhibited robust antimicrobial activity against E. rhusiopathiae, and C-terminal domain of LysP11 bound specifically to E. rhusiopathiae. Bacterial resistance to antibiotics, a serious issue in terms of global public health, is one of the leading causes of death today. Thus, new antimicrobial agents are needed to combat pathogens. Recent research suggests that bacteriophages and endolysins derived from bacteriophages are potential alternatives to traditional antibiotics. Here, we examined the antimicrobial activity of LysP11, which is encoded by Propionibacterium phage P1.1 and comprises an N-terminal amidase-2 domain and a C-terminal domain with no homology to other bacteriophage endolysins. LysP11 was produced in Nicotiana benthamiana (N. benthamiana) using an Agrobacterium-mediated transient expression strategy. LysP11 was purified on microcrystalline cellulose-binding resin after attachment of the Clostridium thermocellum-derived family 3 cellulose-binding domain as an affinity tag. The affinity tag was removed using the small ubiquitin-related modifier (SUMO) domain and SUMO-specific protease. Plant-produced LysP11 showed strong antimicrobial activity toward Erysipelothrix rhusiopathiae (E. rhusiopathiae), mediated via lysis of the cell wall. Lytic activity was optimal at pH 8.0-9.0 (37 °C) and increased at higher concentrations of NaCl up to 400 mM. Furthermore, the C-terminal domain of LysP11 bound specifically to the E. rhusiopathiae cell wall. Based on these results, we propose that LysP11 is a potential candidate antimicrobial agent against E. rhusiopathiae.

Recent omics technologies and their emerging applications for personalised medicine.

A major objective of 'omics' technologies is to understand genetic causality of complex traits of human diseases. High-throughput omics technologies and their application to medicine open up remarkable opportunities for realising optimised medical treatment for individuals. Because many major breakthrough and discoveries in this field have been driven by the development of new omics technologies, in this review, the authors aim to provide an in-depth description of their underlying principles as a foundation of developing another new omics technology, and to introduce their emerging applications for personalised medicine. The systems biology approach is then introduced as a future direction towards actionable personalised medicine.