Ectopic expression of BOTRYTIS SUSCEPTIBLE1 reveals its function as a positive regulator of wound-induced cell death and plant susceptibility to Botrytis

Engineering scutellarin biosynthesis in Artemisia annua

KEY MESSAGE

Heterologous synthesis of scutellarin was successfully achieved in Artemisia annua by supplementing missing enzymes and optimizing flavone 6 hydroxylase in the biosynthetic pathway after identifying two crucial precursors in wild type plants. Artemisia annua, a plant renowned for its antimalarial properties, harbors a diverse array of terpenoids, phenols and other natural products along with their respective precursors. Engineering A. annua plants through synthetic biology holds significant promise to produce drugs in scarcity. Herein, we identified two essential precursors of scutellarin, an ingredient known for its remarkable therapeutic efficacy in treating cerebrovascular and cardiovascular diseases, within wild-type A. annua plants. To facilitate the heterologous synthesis of this bioactive compound in A. annua, we co-expressed three key genes derived from the original host, Erigeron breviscapus: the flavone synthase II gene (EbFSII), the flavonoid-7-O-glucuronosyltransferase gene (EbF7GAT), and the flavone-6-hydroxylase gene (EbF6H). These engineered plants successfully synthesized scutellarin at levels ranging from 0.18 to 0.24 mg/g DW. Furthermore, the introduction of the flavone-6-hydroxylase gene from Scutellaria baicalensis (SbF6H), which demonstrated superior catalytic activity, significantly increased scutellarin generation, achieving concentrations of up to 0.64 mg/g DW. Notably, the insertion of these exogenous genes did not negatively affect the synthesis of artemisinin and its derivatives in A. annua. These findings suggest that A. annua offers a formidable foundation for the biosynthesis of scutellarin. Additionally, the results imply that enhancing the activity of critical enzymes boosts the yield of the valuable terminal products.

Diverse roles of MYB transcription factors in plants

MYB transcription factors (TFs), one of the largest TF families in plants, are involved in various plant-specific processes as the central regulators, such as in phenylpropanoid metabolism, cell cycle, formation of root hair and trichome, phytohormones responses, reproductive growth and abiotic or biotic stress responses. Here we summarized multiple roles and explained the molecular mechanisms of MYB TFs in plant development and stress adaptation. The exploration of MYB TFs contributes to a better comprehension of molecular regulation in plant development and environmental adaptability.

The oilseed rape R2R3-type BnaMYB78 transcription factor regulates leaf senescence by modulating PCD and chlorophyll degradation

Leaf senescence is the final stage of plant growth and development, characterized by chlorophyll degradation, organelle disintegration, and nutrient redistribution and utilization. This stage involves a complex and precise regulatory network, and the underlying mechanisms are not fully understood. Oilseed rape (Brassica napus L.) is one of the most important oil crops in China and globally. Therefore, mining and studying the key factors modulating leaf senescence and abscission in oilseed rape is of great importance to improve its yielding and nutrient use efficiency. In this study, we report that BnaMYB78 positively regulates leaf senescence in oilseed rape. As a transcriptional activator located in the nucleus, BnaMYB78 can bind to the SMRE7 (A/G)CC(T/A)AA(C/T) cis-element in vitro and positively regulate the expression of BnaPBS3, BnaMC9, and BnaNYC1 in oilseed rape. Overexpression of BnaMYB78 leads to chlorophyll degradation and premature leaf senescence in both Arabidopsis thaliana and oilseed rape. During this process, the expression of several genes associated with salicylic acid (SA) synthesis, chlorophyll metabolism, and senescence-associated genes (SAGs) was upregulated, including BnaPPH, BnaSAG14, BnaMC9, BnaPBS3, BnaNYC1, and BnaICS1, which facilitate the progression of programmed cell death (PCD). Further analyses demonstrated that BnaMYB78 activates the promoter activities of BnaMC9, BnaPBS3, and BnaNYC1 in a dual-luciferase reporter assay. Electrophoretic mobility shift assays (EMSAs) and chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) assays revealed that BnaMYB78 directly binds to the promoter regions of these downstream target genes. In summary, our data demonstrate that BnaMYB78 modulates cell death and leaf senescence.

Dual RNA-seq reveals distinct families of co-regulated and structurally conserved effectors in Botrytis cinerea infection of Arabidopsis thaliana

BACKGROUND

Botrytis cinerea is a broad-host-range pathogen causing gray mold disease and significant yield losses of numerous crops. However, the mechanisms underlying its rapid invasion and efficient killing of plant cells remain unclear.

RESULTS

In this study, we elucidated the dynamics of B. cinerea infection in Arabidopsis thaliana by live cell imaging and dual RNA sequencing. We found extensive transcriptional reprogramming events in both the pathogen and the host, which involved metabolic pathways, signaling cascades, and transcriptional regulation. For the pathogen, we identified 591 candidate effector proteins (CEPs) and comprehensively analyzed their co-expression, sequence similarity, and structural conservation. The results revealed temporal co-regulation patterns of these CEPs, indicating coordinated deployment of effectors during B. cinerea infection. Through functional screening of 48 selected CEPs in Nicotiana benthamiana, we identified 11 cell death-inducing proteins (CDIPs) in B. cinerea.

CONCLUSIONS

The findings provide important insights into the transcriptional dynamics and effector biology driving B. cinerea pathogenesis. The rapid infection of this pathogen involves the temporal co-regulation of CEPs and the prominent role of CDIPs in host cell death. This work highlights significant changes in gene expression associated with gray mold disease, underscoring the importance of a diverse repertoire of effectors crucial for successful infection.

Grapevine gray mold disease: infection, defense and management

Grapevine (Vitis vinifera L.,) is among the world's leading fruit crops. The production of grapes is severely affected by many diseases including gray mold, caused by the necrotrophic fungus Botrytis cinerea. Although all Vitis species can be hosts for B. cinerea, V. vinifera are particularly susceptible. Accordingly, this disease poses a significant threat to the grape industry and causes substantial economic losses. Development of resistant V. vinifera cultivars has progressed from incidental selection by farmers, to targeted selection through the use of statistics and experimental design, to the employment of genetic and genomic data. Emerging technologies such as marker-assisted selection and genetic engineering have facilitated the development of cultivars that possess resistance to B. cinerea. A promising method involves using the CRISPR/Cas9 system to induce targeted mutagenesis and develop genetically modified non-transgenic crops. Hence, scientists are now engaged in the active pursuit of identifying genes associated with susceptibility and resistance. This review focuses on the known mechanisms of interaction between the B. cinerea pathogen and its grapevine host. It also explores innate immune systems that have evolved in V. vinifera, with the objective of facilitating the rapid development of resistant grapevine cultivars.

Challenges and Opportunities Arising from Host-Botrytis cinerea Interactions to Outline Novel and Sustainable Control Strategies: The Key Role of RNA Interference

The necrotrophic plant pathogenic fungus Botrytis cinerea (Pers., 1794), the causative agent of gray mold disease, causes significant losses in agricultural production. Control of this fungal pathogen is quite difficult due to its wide host range and environmental persistence. Currently, the management of the disease is still mainly based on chemicals, which can have harmful effects not only on the environment and on human health but also because they favor the development of strains resistant to fungicides. The flexibility and plasticity of B. cinerea in challenging plant defense mechanisms and its ability to evolve strategies to escape chemicals require the development of new control strategies for successful disease management. In this review, some aspects of the host-pathogen interactions from which novel and sustainable control strategies could be developed (e.g., signaling pathways, molecules involved in plant immune mechanisms, hormones, post-transcriptional gene silencing) were analyzed. New biotechnological tools based on the use of RNA interference (RNAi) are emerging in the crop protection scenario as versatile, sustainable, effective, and environmentally friendly alternatives to the use of chemicals. RNAi-based fungicides are expected to be approved soon, although they will face several challenges before reaching the market.

BrMYB108 confers resistance to Verticillium wilt by activating ROS generation in Brassica rapa

Increasing plant resistance to Verticillium wilt (VW), which causes massive losses of Brassica rapa crops, is a challenge worldwide. However, few causal genes for VW resistance have been identified by forward genetic approaches, resulting in limited application in breeding. We combine a genome-wide association study in a natural population and quantitative trait locus mapping in an F2 population and identify that the MYB transcription factor BrMYB108 regulates plant resistance to VW. A 179 bp insertion in the BrMYB108 promoter alters its expression pattern during Verticillium longisporum (VL) infection. High BrMYB108 expression leads to high VL resistance, which is confirmed by disease resistance tests using BrMYB108 overexpression and loss-of-function mutants. Furthermore, we verify that BrMYB108 confers VL resistance by regulating reactive oxygen species (ROS) generation through binding to the promoters of respiratory burst oxidase genes (Rboh). A loss-of-function mutant of AtRbohF in Arabidopsis shows significant susceptibility to VL. Thus, BrMYB108 and its target ROS genes could be used as targets for genetic engineering for VL resistance of B. rapa.

A 6-year study on the mortality dynamics of sprouts germinated on Schima superba after a severe ice storm in southern China

Introduction

Natural disturbances modify forest structure by affecting regeneration dynamics and can change main ecosystem functions. An ice storm unusually took place in southern China in early 2008, which caused huge damage to forests. Resprouting of woody plants in a subtropical forest has received little attention. The role of survival time and mortality has been assessed for newsprouts after an ice storm.

Methods

In this study, damage types, in addition to the annual number and mortality rates of sprouts for all tagged and sampled resprouted Chinese gugertree (Schima superba Gardner & Champ.) individuals more than or equal to 4 cm in basal diameter (BD), were monitored. A total of six plots (20 m × 20 m) wererecorded in a subtropical secondary forest dominated by S. superba in Jianglang Mountain, China. This investigation had been conducted for six consecutive years.

Results

The results showed that the survival rates of the sprouts were dependent on the year they sprouted. The earlier the year they boomed, the lower the mortality. The sprouts produced in 2008 were of the highest vitality and survival rates. Sprouts of the decapitated trees exhibited a better survival rate than those of uprooted or leaning trees. Sprouting position also plays a role in regeneration. Sprouts at the basal trunks of uprooted trees and the sprouts at the upper trunksof the decapitated trees exhibited the lowest mortality. The relationship between the accumulative mortality rate and the average diameter of new sprouts isaffected by damage types.

Discussion

We reported the mortality dynamics of sproutsin a subtropical forest after a rare natural disaster. This information could serve asa reference for the construction of a branch sprout dynamic model ormanagement of forest restoration after ice storms.

Candidate gene discovery of Botrytis cinerea resistance in grapevine based on QTL mapping and RNA-seq

Grape gray mold disease (Botrytis cinerea) is widespread during grape production especially in Vitis vinifera and causes enormous losses to the grape industry. In nature, the grapevine cultivar 'Beta ' (Vitis riparia × Vitis labrusca) showed high resistance to grape gray mold. Until now, the candidate genes and their mechanism of gray mold resistance were poorly understood. In this study, we firstly conducted quantitative trait locus (QTL) mapping for grape gray mold resistance based on two hybrid offspring populations that showed wide separation in gray mold resistance. Notably, two stable QTL related to gray mold resistance were detected and located on linkage groups LG2 and LG7. The phenotypic variance ranged from 6.86% to 13.70% on LG2 and 4.40% to 11.40% on LG7. Combined with RNA sequencing (RNA-seq), one structural gene VlEDR2 (Vitvi02g00982) and three transcription factors VlERF039 (Vitvi00g00859), VlNAC047 (Vitvi08g01843), and VlWRKY51 (Vitvi07g01847) that may be involved in VlEDR2 expression and grape gray mold resistance were selected. This discovery of candidate gray mold resistance genes will provide an important theoretical reference for grape gray mold resistance mechanisms, research, and gray mold-resistant grape cultivar breeding in the future.