Receptor-Like Kinase (RLK) as a candidate gene conferring resistance to Hemileia vastatrix in coffee

Abstract

The biotrophic fungus Hemileia vastatrix causes coffee leaf rust (CLR), one of the most devastating diseases in Coffea arabica. Coffee, like other plants, has developed effective mechanisms to recognize and respond to infections caused by pathogens. Plant resistance gene analogs (RGAs) have been identified in certain plants as candidates for resistance (R) genes or membrane receptors that activate the R genes. The RGAs identified in different plants possess conserved domains that play specific roles in the fight against pathogens. Despite the importance of RGAs, in coffee plants these genes and other molecular mechanisms of disease resistance are still unknown. This study aimed to sequence and characterize candidate genes from coffee plants with the potential for involvement in resistance to H. vastatrix. Sequencing was performed based on a library of bacterial artificial chromosomes (BAC) of the coffee clone 'Híbrido de Timor' (HdT) CIFC 832/2 and screened using a functional marker. Two RGAs, HdT_ LRR_RLK1 and HdT_LRR_RLK2, containing the motif of leucine-rich repeat-like kinase (LRR-RLK) were identified. Based on the presence or absence of the HdT_LRR_RLK2 RGA in a number of differential coffee clones containing different combinations of the rust resistance gene, these RGAs did not correspond to any resistance gene already characterized (S H 1-9). These genes were also analyzed using qPCR and demonstrated a major expression peak at 24 h after inoculation in both the compatible and incompatible interactions between coffee and H. vastatrix. These results are valuable information for breeding programs aimed at developing CLR-resistant cultivars, in addition to enabling a better understanding of the interactions between coffee and H. vastatrix.

An Overview of the Mechanisms Involved in Coffee-Hemileia vastatrix Interactions: Plant and Pathogen Perspectives

“…Plant perception of the pathogen invasion follows a surveillance system assembled in a multilayer fashion to identify apoplastic and cytoplasmatic pathogen effectors. At the early stages of the infection process, some of the multi-domain recognition receptors are activated in the incompatible coffee-H. vastatrix interaction (RLK and LRR-RLK2, NBS-LRR), suggesting their role in the host resistance response [22,140,150,152,153]. Nevertheless, in some other incompatible coffee-H. vastatrix interactions, this may not be the case [143,152], indicating that immune receptors can have different mechanisms for ligand binding and receptor complex formation, which can modulate the activation, intensity and duration of plant immune responses [162].…”

“…Coffee-H. vastatrix interactions are governed by the Flor's gene-for-gene relationship, and the resistance of coffee plants is conditioned at least by nine major dominant genes (S H 1-S H 9) singly or associated [11,19,20], although other major and minor genes may also be involved [11,21,22]. The use of coffee-resistant varieties is considered the most sustainable, efficient, and eco-friendly strategy to control this disease.…”

LysM receptors in Coffea arabica: Identification, characterization, and gene expression in response to Hemileia vastatrix

“…vastatrix in stomata of coffee leaves, both in resistant and susceptible genotypes and at 48 hpi the presence of haustoria is already observed [ 75 – 77 ]. In addition, a LRR receptor-like kinase described in this pathosystem has a peak expression at 24 hpi in compatible and incompatible interactions [ 78 ], thus suggesting that the signal exchange between the two organisms is already occurring in this period.…”

LysM receptors in Coffea arabica: identification, characterization, and gene expression in response to Hemileia vastatrix

“…The experiments showed that at 24 hpi it is already possible to detect the penetration of the hypha produced by the appressorium of H. vastatrix in stomata of coffee leaves, both in resistant and susceptible genotypes and at 48 hpi the presence of haustoria is already observed [76–78]. In addition, a LRR receptor-like kinase described in this pathosystem has a peak expression at 24 hpi in compatible and incompatible interactions [79], thus suggesting that the signal exchange between the two organisms is already occurring in this period.…”