Arabidopsis Phospholipase Dδ Is Involved in Basal Defense and Nonhost Resistance to Powdery Mildew Fungi  

Abstract

Plants have evolved a complex array of defensive responses against pathogenic microorganisms. Recognition of microbes initiates signaling cascades that activate plant defenses. The membrane lipid phosphatidic acid, produced by phospholipase D (PLD), has been shown to take part in both abiotic and biotic stress signaling. In this study, the involvement of PLD in the interaction between Arabidopsis (Arabidopsis thaliana) and the barley powdery mildew fungus Blumeria graminis f. sp. hordei (Bgh) was investigated. This nonadapted pathogen is normally resisted by a cell wall-based defense, which stops the fungal hyphae from penetrating the epidermal cell wall. Chemical inhibition of phosphatidic acid production by PLD increased the penetration rate of Bgh spores on wild-type leaves. The analysis of transfer DNA knockout lines for all Arabidopsis PLD genes revealed that PLDd is involved in penetration resistance against Bgh, and chemical inhibition of PLDs in plants mutated in PLDd indicated that this isoform alone is involved in Bgh resistance. In addition, we confirmed the involvement of PLDd in penetration resistance against another nonadapted pea powdery mildew fungus, Erysiphe pisi. A green fluorescent protein fusion of PLDd localized to the plasma membrane at the Bgh attack site, where it surrounded the cell wall reinforcement. Furthermore, in the pldd mutant, transcriptional up-regulation of early microbe-associated molecular pattern response genes was delayed after chitin stimulation.In conclusion, we propose that PLD is involved in defense signaling in nonhost resistance against powdery mildew fungi and put PLDd forward as the main isoform participating in this process.

From Chaos to Harmony: Responses and Signaling upon Microbial Pattern Recognition

“…It is possible that different MAMPs induce PA production via distinct pathways yet the genetic evidence for the involvement of PA in PTI signaling remains elusive. A mutation in PLD isoform PLDδ displays delayed defense gene induction upon chitin treatment and compromised resistance against barley powdery mildew (121). In addition, PA exhibits extensive cross-talk with other signaling molecules (Figure 1).…”

Functional Characterization of the N-Terminal C2 Domain fromArabidopsis thalianaPhospholipase Dαand Dβ

“…All these PLDs have been demonstrated to play central roles in seed germination [7, 8], growth and biomass accumulation [9], stress [10, 11], defense [12], and wound healing [13]. Based on their gene architecture, their sequence similarities, and their biochemical properties, these PLDs can be grouped into two major categories.…”

“…Nevertheless, both of these isoforms have been demonstrated to hydrolyze PC, PG, and N-acylphosphatidylethanolamine in the presence of PIP 2 and 50  μ M of Ca 2+ , at a physiological pH [16]. Concerning the δ -type PLD, 2 spliced variant isoforms have been identified so far and shown to be involved in defense signaling [12] and freezing tolerance [25]. Similarly to β - and γ -type PLDs, δ -type PLD hydrolyzes PC in the presence of PIP 2 and 50 to 100  μ M of Ca 2+ but is also stimulated by oleate [26].…”

Host to a Stranger: Arabidopsis and Fusarium Ear Blight

“…Therefore, Arabidopsis has been used to study the determinants of non-host resistance. Genetic screens using this pathosystem have identified several genes required for non-host resistance to these pathogens, including the PEN (PENETRATION) gene suite and PLDd (PHOSPHOLIPASE Dd) [83][84][85]. …”