EDS1-interacting J protein 1 is an essential negative regulator of plant innate immunity in Arabidopsis

LESION SIMULATING DISEASE 3 regulates disease resistance via fine-tuning histone acetylation in cassava

Bacterial blight seriously affects the growth and production of cassava (Manihot esculenta Crantz), but disease resistance genes and the underlying molecular mechanism remain unknown. In this study, we found that LESION SIMULATING DISEASE 3 (MeLSD3) is essential for disease resistance in cassava. MeLSD3 physically interacts with SIRTUIN 1 (MeSRT1), inhibiting MeSRT1-mediated deacetylation modification at the acetylation of histone 3 at K9 (H3K9Ac). This leads to increased H3K9Ac levels and transcriptional activation of SUPPRESSOR OF BIR1 (SOBIR1) and FLAGELLIN-SENSITIVE2 (FLS2) in pattern-triggered immunity, resulting in immune responses in cassava. When MeLSD3 was silenced, the release of MeSRT1 directly decreased H3K9Ac levels and inhibited the transcription of SOBIR1 and FLS2, leading to decreased disease resistance. Notably, DELLA protein GIBBERELLIC ACID INSENSITIVE 1 (MeGAI1) also interacted with MeLSD3, which enhanced the interaction between MeLSD3 and MeSRT1 and further strengthened the inhibition of MeSRT1-mediated deacetylation modification at H3K9Ac of defense genes. In summary, this study illustrates the mechanism by which MeLSD3 interacts with MeSRT1 and MeGAI1, thereby mediating the level of H3K9Ac and the transcription of defense genes and immune responses in cassava.

Engineering plant immune circuit: walking to the bright future with a novel toolbox

Plant pathogens destroy crops and cause severe yield losses, leading to an insufficient food supply to sustain the human population. Apart from relying on natural plant immune systems to combat biological agents or waiting for the appropriate evolutionary steps to occur over time, researchers are currently seeking new breakthrough methods to boost disease resistance in plants through genetic engineering. Here, we summarize the past two decades of research in disease resistance engineering against an assortment of pathogens through modifying the plant immune components (internal and external) with several biotechnological techniques. We also discuss potential strategies and provide perspectives on engineering plant immune systems for enhanced pathogen resistance and plant fitness.

Genome-Wide Analysis of Soybean Lateral Organ Boundaries Domain Gene Family Reveals the Role in Phytophthora Root and Stem Rot

The plant-specific lateral organ boundaries (LOB) domain (LBD) proteins, a family of transcription factors, play important roles in plant growth and development, as well as in responses to various stresses. However, little is known about the functions of LBD genes in soybean (Glycine max). In this study, we investigated the evolution and classification of the LBD family in soybean by a phylogenetic tree of the LBD gene family from 16 species. Phylogenetic analysis categorized these proteins into two classes (Class I and Class II) with seven subgroups. Moreover, we found that all the 18 LBD ancestors in angiosperm were kept in soybean, common bean genomes, and genome-wide duplication, suggesting the main force for the expansion of LBD from common bean to soybean. Analysis of gene expression profiling data indicated that 16 GmLBD genes were significantly induced at different time points after inoculation of soybean plants (cv. Huachun 6) with Phytophthora sojae (P. sojae). We further assessed the role of four highly upregulated genes, GmLBD9, GmLBD16, GmLBD23, and GmLBD88, in plant defense in soybean hairy roots using the transient overexpression and knockdown assays. The results showed that GmLBD9 and GmLBD23 negatively regulate plant immunity against P. sojae, whereas GmLBD16 and GmLBD88 positively manipulate plant immunity against P. sojae. Collectively, our findings expand our knowledge of the origin and evolution of the GmLBD gene family in soybean and promote the potential application of these genes in soybean genetic improvement.

GhENODL6 Isoforms from the Phytocyanin Gene Family Regulated Verticillium Wilt Resistance in Cotton

Verticillium wilt (VW), a fungal disease caused by Verticillium dahliae, currently devastates cotton fiber yield and quality seriously, yet few resistance germplasm resources have been discovered in Gossypium hirsutum. The cotton variety Nongda601 with suitable VW resistance and high yield was developed in our lab, which supplied elite resources for discovering resistant genes. Early nodulin-like protein (ENODL) is mainly related to nodule formation, and its role in regulating defense response has been seldom studied. Here, 41 conserved ENODLs in G. hirsutum were identified and characterized, which could divide into four subgroups. We found that GhENODL6 was upregulated under V. dahliae stress and hormonal signal and displayed higher transcript levels in resistant cottons than the susceptible. The GhENODL6 was proved to positively regulate VW resistance via overexpression and gene silencing experiments. Overexpression of GhENODL6 significantly enhanced the expressions of salicylic acid (SA) hormone-related transcription factors and pathogenicity-related (PR) protein genes, as well as hydrogen peroxide (H₂O₂) and SA contents, resulting in improved VW resistance in transgenic Arabidopsis. Correspondingly, in the GhENODL6 silenced cotton, the expression levels of both phenylalanine ammonia lyase (PAL) and 4-coumarate-CoA ligase (4CL) genes significantly decreased, leading to the reduced SA content mediating by the phenylalanine ammonia lyase pathway. Taken together, GhENODL6 played a crucial role in VW resistance by inducing SA signaling pathway and regulating the production of reactive oxygen species (ROS). These findings broaden our understanding of the biological roles of GhENODL and the molecular mechanisms underlying cotton disease resistance.

Transcriptional Coactivators: Driving Force of Plant Immunity

Salicylic acid (SA) is a plant defense signal that mediates local and systemic immune responses against pathogen invasion. However, the underlying mechanism of SA-mediated defense is very complex due to the involvement of various positive and negative regulators to fine-tune its signaling in diverse pathosystems. Upon pathogen infections, elevated level of SA promotes massive transcriptional reprogramming in which Non-expresser of PR genes 1 (NPR1) acts as a central hub and transcriptional coactivator in defense responses. Recent findings show that Enhanced Disease Susceptibility 1 (EDS1) also functions as a transcriptional coactivator and stimulates the expression of PR1 in the presence of NPR1 and SA. Furthermore, EDS1 stabilizes NPR1 protein level, while NPR1 sustains EDS1 expression during pathogenic infection. The interaction of NPR1 and EDS1 coactivators initiates transcriptional reprogramming by recruiting cyclin-dependent kinase 8 in the Mediator complex to control immune responses. In this review, we highlight the recent breakthroughs that considerably advance our understanding on how transcriptional coactivators interact with their functional partners to trigger distinct pathways to facilitate immune responses, and how SA accumulation induces dynamic changes in NPR1 structure for transcriptional reprogramming. In addition, the functions of different Mediator subunits in SA-mediated plant immunity are also discussed in light of recent discoveries. Taken together, the available evidence suggests that transcriptional coactivators are essential and potent regulators of plant defense pathways and play crucial roles in coordinating plant immune responses during plant-pathogen interactions.