Genome-Wide Identification of Rapid Alkalinization Factor Family in Brassica napus and Functional Analysis of BnRALF10 in Immunity to Sclerotinia sclerotiorum

Abstract

Rapid alkalinization factors (RALFs) were recently reported to be important players in plant immunity. Nevertheless, the signaling underlying RALF-triggered immunity in crop species against necrotrophic pathogens remains largely unknown. In this study, RALF family in the important oil crop oilseed rape (Brassica napus) was identified and functions of BnRALF10 in immunity against the devastating necrotrophic pathogen Sclerotinia sclerotiorum as well as the signaling underlying this immunity were revealed. The oilseed rape genome carried 61 RALFs, half of them were atypical, containing a less conserved YISY motif and lacking a RRXL motif or a pair of cysteines. Family-wide gene expression analyses demonstrated that patterns of expression in response to S. sclerotiorum infection and DAMP and PAMP treatments were generally RALF- and stimulus-specific. Most significantly responsive BnRALF genes were expressionally up-regulated by S. sclerotiorum, while in contrast, more BnRALF genes were down-regulated by BnPep5 and SsNLP1. These results indicate that members of BnRALF family are likely differentially involved in plant immunity. Functional analyses revealed that BnRALF10 provoked diverse immune responses in oilseed rape and stimulated resistance to S. sclerotiorum. These data support BnRALF10 to function as a DAMP to play a positive role in plant immunity. BnRALF10 interacted with BnFER. Silencing of BnFER decreased BnRALF10-induced reactive oxygen species (ROS) production and compromised rape resistance to S. sclerotiorum. These results back BnFER to be a receptor of BnRALF10. Furthermore, quantitative proteomic analysis identified dozens of BnRALF10-elicited defense (RED) proteins, which respond to BnRALF10 in protein abundance and play a role in defense. Our results revealed that BnRALF10 modulated the abundance of RED proteins to fine tune plant immunity. Collectively, our results provided some insights into the functions of oilseed rape RALFs and the signaling underlying BnRALF-triggered immunity.

Tomato LysM receptor kinase 4 mediates chitin-elicited fungal resistance in both leaves and fruit

“…S7). P-loop subdomain I, RD domain in subdomain VIa, and DFG domain in subdomain VII are generally regarded as essential for kinase activity [ 49 ]. Similar to AtLYK4 and AtLYK5, SlLYK4 lacks these critical amino acids, suggesting that SlLYK4 might be a kinase-inactive protein.…”

Glutamate Receptor-like (GLR) Family in Brassica napus: Genome-Wide Identification and Functional Analysis in Resistance to Sclerotinia sclerotiorum

“…The parameters were as follows: the maximum number of motifs was set to 12, the motif width ranged from 6 to 50 (inclusive), and the site distribution was limited to 0 or 1 occurrence (of a contributing motif site) per sequence. Logo motif analysis was also performed to demonstrate the conservativeness of each group of BnGLR proteins using the weblogo3 (v3.7) platform [ 36 ].…”

“…Brassica napus plants were grown in growth cabinets at 23 °C under a 14 h/10 h light/dark photoperiod [ 36 ]. All Arabidopsis thaliana plants used in this study were of Col-0 ecotype background and were grown at 16 h photoperiod and 70% humidity at 21 ± 1 °C in the growth chamber [ 44 ].…”

“…Fresh sclerotia of Ss strain UF1 were cultured at 23 °C on potato dextrose agar medium (PDA) to produce mycelia, which were transferred to new PDA plates and grown for 2 days. The PDA plugs containing young Ss mycelia were punched to inoculate the leaves of 30 d old plants [ 36 ]. Area of disease lesions was measured using the ImageJ (v1.54e) software [ 36 ].…”

“…The PDA plugs containing young Ss mycelia were punched to inoculate the leaves of 30 d old plants [ 36 ]. Area of disease lesions was measured using the ImageJ (v1.54e) software [ 36 ]. For disease resistance evaluation, at least five plants for each genotype were examined and the experiments were conducted three times independently.…”