The Arabidopsis Pleiotropic Drug Resistance Transporters PEN3 and PDR12 Mediate Camalexin Secretion for Resistance to Botrytis cinerea

Abstract

Plant defense often depends on the synthesis and targeted delivery of antimicrobial metabolites at pathogen contact sites. The pleiotropic drug resistance (PDR) transporter PENETRATION3 (PEN3)/PDR8 in Arabidopsis (Arabidopsis thaliana) has been implicated in resistance to a variety of fungal pathogens. However, the antimicrobial metabolite(s) transported by PEN3 for extracellular defense remains unidentified. Here, we report that PEN3 functions redundantly with another PDR transporter (PDR12) to mediate the secretion of camalexin, the major phytoalexin in Arabidopsis. Consistent with this, the pen3 pdr12 double mutants exhibit dramatically enhanced susceptibility to the necrotrophic fungus Botrytis cinerea as well as severe hypersensitivity to exogenous camalexin. PEN3 and PDR12 are transcriptionally activated upon B. cinerea infection, and their expression is regulated by the mitogen-activated protein kinase 3 (MPK3) and MPK6, and their downstream WRKY33 transcription factor. Further genetic analysis indicated that PEN3 and PDR12 contribute to B. cinerea resistance through exporting not only camalexin but also other unidentified metabolite(s) derived from Trp metabolism, suggesting that PEN3 and PDR12 have multiple functions in Arabidopsis immunity via transport of distinct Trp metabolic products.

Co‐regulation of indole glucosinolates and camalexin biosynthesis by CPK5/CPK6 and MPK3/MPK6 signaling pathways

“…In response to pathogen infection, both CPK and MAPK signaling pathways can be rapidly activated (Hake and Romeis 2019). Our previous reports and this study reveal that both CPK5/CPK6 and MPK3/MPK6 are involved in regulating B. cinerea-induced 4MI3G and camalexin (Ren et al 2008;Xu et al 2016;He et al 2019). What is the relationship between these two pathways in this process?…”

Genome-wide characterization and expression profiling of MAPK cascade genes in Salvia miltiorrhiza reveals the function of SmMAPK3 and SmMAPK1 in secondary metabolism

“…8), which have been reported to regulate the synthesis and accumulation of secondary metabolites [57,59,[67][68][69]. In A. thaliana, MAPKK9 promotes ethylene and camalexin biosynthesis [70], and both AtMPK3 and AtMPK6, which are highly involved in the plant response to biotic [71][72][73][74][75] and abiotic stress [21,54,76] and the regulation of ETH [17,26,33], SA [29,75] and JA [33,77] production, are activated by the upstream regulatory MAPK kinases AtMKK4 and AtMKK5 [78,79], which are in turn regulated by the upstream MAPKK kinase AtMEKK1 [80]. Such interspecific similarity in MAPK function and interspecific differences in the architecture of MAPK cascades explain the conservation and variability of gene evolution.…”

The formation of a camalexin-biosynthetic metabolon

“…CYP79B2 and Arabidopsis P450 Reductase1 (ATR1) were detected in the co-IP, but the respective enrichments (4.5-fold, P 5 0.17 and 5.0-fold, P 5 0.022, respectively) were below the threshold of significance, pointing to a weak or transient interaction with the observed CYP71B15containing protein complex. Interestingly, PDR12/ABCG40, which was recently identified as a camalexin transporter (He et al, 2019), was significantly enriched (7.8-fold, P 5 0.00029), suggesting CYP71B15pro:CYP71B15-GFP-expressing plants were inoculated with spores of B. cinerea, A. brassicicola, or E. cruciferarum, and the expression of CYP71B15-GFP at fungal infections sites was detected. that the biosynthesis and transport of camalexin might be physically linked to some extent.…”