Transient expression of the <i>Arabidopsis thaliana</i> callose synthase PMR4 increases penetration resistance to powdery mildew in barley

Abstract

Localized cell wall thickenings, so called papillae, are a common plant defense response to fungal attack at sites of penetration of the plant cell. The major constituent of papillae is callose, a (1,3)-β-glucan polymer, which contributes to slowing or blocking the invading fungal hyphae. In the model plant Arabidopsis thaliana, we could recently show that the overexpression of PMR4 (POWDERY MILDEW RESITANT 4), which encodes a stress induced callose synthase, results in complete powdery mildew resistance. To evaluate if these findings are also transferable to monocot crops, we transiently expressed PMR4 under control of the 35S promoter in leaves of barley (Hordeum vulgare) seedlings, which were subsequently inoculated with the virulent powdery mildew Blumeria graminis f. sp. hordei. Fusion of the green fluorescent protein (GFP) to PMR4 allowed the identification of successfully transformed barley cells, which showed an increased penetration resistance to B. graminis compared to control cells that express only GFP. PMR4-GFP localized in a similar pattern at the site of attempted fungal penetration as observed in A. thaliana, which suggests that similar transport mechanisms of the callose synthase might exist in dicot and monocot plants.

The Coiled-Coil and Nucleotide Binding Domains of BROWN PLANTHOPPER RESISTANCE14 Function in Signaling and Resistance against Planthopper in Rice

“…Several RLCKs are thought to play pivotal roles in plant defense (Martin et al, 1994;Swiderski and Innes, 2001;Zhang et al, 2010;Shi et al, 2013;Liu et al, 2011;Feng et al, 2012;Shinya et al, 2014;Yamaguchi et al, 2013;Dubouzet et al, 2011;Wang et al, 2015b;Zhou et al, 2016) and are thought to be involved in connecting signal perception by RLKs in the plasma membrane to downstream intracellular signal transduction systems. Callose synthases such as LOC_Os01g67364.1 perform callose biosynthesis in plants (Xie et al, 2011), and there is considerable evidence that they function in preventing penetration by herbivores (Enrique et al, 2011;Blümke et al, 2013Blümke et al, , 2014Ellinger et al, 2013). We found that the promoters of RLCK281 and LOC_Os01g67364.1 were associated with WRKY46 and WRKY72; the presence of the CC, NB, and CN domains or FL BPH14 enhanced the association between the WRKYs and the promoters of RLCK281 and LOC_Os01g67364.1 in rice.…”

Integrated Metabolo-Transcriptomics Reveals Fusarium Head Blight Candidate Resistance Genes in Wheat QTL-Fhb2

“…Callose synthase 5 ( CalS5 ) in Arabidopsis thaliana plays a predominant role in the synthesis of the callose wall and callose plugs, and containment of powdery mildew hyphae in Arabidopsis [ 80 ]. Arabidopsis thaliana callose synthase PMR4 expression in barley increased penetration resistance to powdery mildew [ 81 ]. Hence, we consider callose synthase as one of the integral candidates in FHB defense.…”

Differential accumulation of callose, arabinoxylan and cellulose in nonpenetrated versus penetrated papillae on leaves of barley infected with Blumeria graminis f. sp. hordei

“…The inhibition of Arabidopsis papillary callose deposition through disruption of the callose synthase gene, GLUCAN SYNTHASE‐LIKE 5 (GSL5) , also known as POWDERY MILDEW RESISTANT 4 (PMR4) , showed a marginally decreased penetration rate in the Arabidopsis– Golovinomyces cichoracearum interaction (Jacobs et al ., ) and in the Arabidopsis– Erysiphe cichoracearum interaction (Nishimura et al ., ). Conversely, when the PMR4 gene is overexpressed, higher and early accumulation of papillary callose occurs and host plants show complete penetration resistance against the well‐adapted pathogens G. cichoracearum (Ellinger et al ., ) and, in the case of barley, Bgh (Blümke et al ., ). Chemical inhibition of papillary callose synthesis also increases the penetration efficiency of fungal pathogens on nonhost grass species including rice ( Oryza sativa ), wheat ( Triticum aestivum ) and oat ( Avena sativa ) (Zeyen et al ., ).…”