Defense, Fast and Slow: Activation of Different MAPK Pathways in Response to Wounding

Role of carbohydrate-active enzymes in brown planthopper virulence and adaptability

Introduction

Herbivorous insects, including the brown planthopper (BPH), Nilaparvata lugens, are among the most damaging pests to agricultural crops worldwide, particularly rice. These insects employ a variety of strategies to overcome plant defenses, including the secretion of carbohydrate-active enzymes (CAZymes) that degrade plant cell walls. While CAZymes are well-studied in other insect species, their role in BPH virulence remains largely unexplored.

Methods

This study aims to address this gap by analyzing CAZymes in 182 insect genomes, followed by a detailed genomic and transcriptomic analysis of BPH.

Results

We identified 644 CAZymes in BPH, including enzymes related to plant cell wall degradation. Through quantitative real-time PCR (RT-qPCR) and subcellular localization experiments, we found that 5 candidate genes exhibited increased expression during feeding on the susceptible rice variety TN1, a well-characterized variety highly susceptible to BPH and these genes were localized to the plasma membrane. Our results suggest that BPH CAZymes play a critical role in the insect's ability to feed and damage rice plants.

Discussion

This study provides valuable insights into the molecular mechanisms underlying insect adaptation and virulence in the co-evolutionary process between plants and herbivorous insects. By exploring the function of pest-related genes in the BPH and examining their differential responses in rice varieties with varying resistance to BPH, we aim to contribute to the development of targeted pest management strategies.

Mitogen-activated protein kinases MPK3 and MPK6 phosphorylate receptor-like cytoplasmic kinase CDL1 to regulate soybean basal immunity

Soybean cyst nematode (SCN; Heterodera glycines Ichinohe), one of the most devastating soybean (Glycine max) pathogens, causes significant yield loss in soybean production. Nematode infection triggers plant defense responses; however, the components involved in the upstream signaling cascade remain largely unknown. In this study, we established that a mitogen-activated protein kinase (MAPK) signaling module, activated by nematode infection or wounding, is crucial for soybeans to establish SCN resistance. GmMPK3 and GmMPK6 directly interact with CDG1-LIKE1 (GmCDL1), a member of the receptor-like cytoplasmic kinase (RLCK) subfamily VII. These kinases phosphorylate GmCDL1 at Thr-372 to prevent its proteasome-mediated degradation. Functional analysis demonstrated that GmCDL1 positively regulates immune responses and promotes SCN resistance in soybeans. GmMPK3-mediated and GmMPK6-mediated phosphorylation of GmCDL1 enhances GmMPK3 and GmMPK6 activation and soybean disease resistance, representing a positive feedback mechanism. Additionally, 2 L-type lectin receptor kinases, GmLecRK02g and GmLecRK08g, associate with GmCDL1 to initiate downstream immune signaling. Notably, our study also unveils the potential involvement of GmLecRKs and GmCDL1 in countering other soybean pathogens beyond nematodes. Taken together, our findings reveal the pivotal role of the GmLecRKs-GmCDL1-MAPK regulatory module in triggering soybean basal immune responses.

Transcriptomic data exploring the effect of agave fructans on the induction of the defense system in avocado fruit

The effect of 20% high degree polymerized agave fructans (HDPAF) on the induction of the defense system in avocado fruits was investigated by transcriptomic analysis at 1, 24 and 72 h after treatment, and the effect of HDPAF on respiration rate and ethylene production was also analyzed. Transcriptomic profiling revealed 5425 differentially expressed genes (DEGs), 55 of which were involved in the pathways related to plant defense response to pathogens. Key genes were associated with phenylpropanoid biosynthesis, mitogen-activated protein signaling, plant hormone signaling, calcium ion signal decoding, and pathogenesis-related proteins. Dysregulated genes involved in ethylene biosynthesis were also identified, and the reduction in ethylene production by HDPAF was corroborated by gas chromatography, where three days of delayed peak production was observed compared to that in water-treated fruits. These results help to understand the mechanism of induction of the avocado defense system by applying HDPAF and support the application of HDPAF as an efficient postharvest treatment to extend the shelf life of the fruit.

Recent Advances in Molecular Mechanism and Breeding Utilization of Brown Planthopper Resistance Genes in Rice: An Integrated Review

Over half of the world's population relies on rice as their staple food. The brown planthopper (Nilaparvata lugens Stål, BPH) is a significant insect pest that leads to global reductions in rice yields. Breeding rice varieties that are resistant to BPH has been acknowledged as the most cost-effective and efficient strategy to mitigate BPH infestation. Consequently, the exploration of BPH-resistant genes in rice and the development of resistant rice varieties have become focal points of interest and research for breeders. In this review, we summarized the latest advancements in the localization, cloning, molecular mechanisms, and breeding of BPH-resistant rice. Currently, a total of 70 BPH-resistant gene loci have been identified in rice, 64 out of 70 genes/QTLs were mapped on chromosomes 1, 2, 3, 4, 6, 8, 10, 11, and 12, respectively, with 17 of them successfully cloned. These genes primarily encode five types of proteins: lectin receptor kinase (LecRK), coiled-coil-nucleotide-binding-leucine-rich repeat (CC-NB-LRR), B3-DNA binding domain, leucine-rich repeat domain (LRD), and short consensus repeat (SCR). Through mediating plant hormone signaling, calcium ion signaling, protein kinase cascade activation of cell proliferation, transcription factors, and miRNA signaling pathways, these genes induce the deposition of callose and cell wall thickening in rice tissues, ultimately leading to the inhibition of BPH feeding and the formation of resistance mechanisms against BPH damage. Furthermore, we discussed the applications of these resistance genes in the genetic improvement and breeding of rice. Functional studies of these insect-resistant genes and the elucidation of their network mechanisms establish a strong theoretical foundation for investigating the interaction between rice and BPH. Furthermore, they provide ample genetic resources and technical support for achieving sustainable BPH control and developing innovative insect resistance strategies.

WRKY transcription factor family in lettuce plant (Lactuca sativa): Genome-wide characterization, chromosome location, phylogeny structures, and expression patterns

WRKY transcription factors (TF) have been identified in many plant species and play critical roles in multiple stages of growth and development and under various stress conditions. As one of the most popular vegetable crops, asparagus lettuce has important medicinal and nutritional value. However, study of WRKY TFs family in asparagus lettuce is limited. With the lettuce (Lactuca sativa L.) genome publication, we identified 76 WRKY TFs and analyzed structural characteristics, phylogenetic relationships, chromosomal distribution, interaction network, and expression profiles. The 76 LsWRKY TFs were phylogenetically classified as Groups I, II (IIa-IIe), and III. Cis element analysis revealed complex regulatory relationships of LsWRKY genes in response to different biological progresses. Interaction network analysis indicated that LsWRKY TFs could interact with other proteins, such as SIB (sigma factor binding protein), WRKY TFs, and MPK. The WRKYIII subfamily genes showed different expression patterns during the progress of asparagus lettuce stem enlargement. According to qRT-PCR analysis, abiotic stresses (drought, salt, low temperature, and high temperature) and phytohormone treatment could induce specific LsWRKYIII gene expression. These results will provide systematic and comprehensive information on LsWRKY TFs and lay the foundation for further clarification of the regulatory mechanism of LsWRKY, especially LsWRKYIII TFs, involved in stress response and the progress of plant growth and development.

A New Approach for Wounding Research: MYC2 Gene Expression and Protein Stability in Wounded Arabidopsis Protoplasts

Wounding is a constant threat to plant survival throughout their lifespan; therefore, understanding the biological responses to wounds at the cellular level is important. The protoplast system is versatile for molecular biology, however, no wounding studies on this system have been reported. We established a new approach for wounding research using mechanically damaged Arabidopsis mesophyll protoplasts. Wounded protoplasts showed typical wounding responses, such as increased MPK6 kinase activity and upregulated JAZ1 expression. We also assessed expression profiles and protein stability of the basic helix-loop-helix transcription factor MYC2 in wounded protoplasts. Promoter activity, gene expression, and protein stability of MYC2 were compromised, but recovered in the early stage of wounding. In the late stage, the promoter activity and expression of MYC2 were increased, but the protein stability was not changed. According to the results of the present study, this new cell-based approach will be of use in various molecular studies on plant wounding.

Genome-Wide Identification and Analysis of MKK and MAPK Gene Families in Brassica Species and Response to Stress in Brassica napus

Mitogen-activated protein kinase (MAPK) cascades are common and conserved signal transduction pathways and play important roles in various biotic and abiotic stress responses and growth and developmental processes in plants. With the advancement of sequencing technology, more systematic genetic information is being explored. The work presented here focuses on two protein families in Brassica species: MAPK kinases (MKKs) and their phosphorylation substrates MAPKs. Forty-seven MKKs and ninety-two MAPKs were identified and extensively analyzed from two tetraploid (B. juncea and B. napus) and three diploid (B. nigra, B. oleracea, and B. rapa) Brassica species. Phylogenetic relationships clearly distinguished both MKK and MAPK families into four groups, labeled A–D, which were also supported by gene structure and conserved protein motif analysis. Furthermore, their spatial and temporal expression patterns and response to stresses (cold, drought, heat, and shading) were analyzed, indicating that BnaMKK and BnaMAPK transcript levels were generally modulated by growth, development, and stress signals. In addition, several protein interaction pairs between BnaMKKs and C group BnaMAPKs were detected by yeast two-hybrid assays, in which BnaMKK3 and BnaMKK9 showed strong interactions with BnaMAPK1/2/7, suggesting that interaction between BnaMKKs and C group BnaMAPKs play key roles in the crosstalk between growth and development processes and abiotic stresses. Taken together, our data provide a deeper foundation for the evolutionary and functional characterization of MKK and MAPK gene families in Brassica species, paving the way for unraveling the biological roles of these important signaling molecules in plants.