Arabidopsis BTB/POZ protein-dependent PENETRATION3 trafficking and disease susceptibility

Abstract

The outermost cell layer of plant roots (epidermis) constantly encounters environmental challenges. The epidermal outer plasma membrane domain harbours the PENETRATION3 (PEN3)/ABCG36/PDR8 ATP-binding cassette transporter that confers non-host resistance to several pathogens. Here, we show that the Arabidopsis ENDOPLASMIC RETICULUM-ARRESTED PEN3 (EAP3) BTB/POZ-domain protein specifically mediates PEN3 exit from the endoplasmic reticulum and confers resistance to a root-penetrating fungus, providing prime evidence for BTB/POZ-domain protein-dependent membrane trafficking underlying disease resistance.The PENETRATION3 (PEN3/ABCG36/PDR8) ATP-binding cassette transporter of Arabidopsis thaliana is a crucial component of preinvasive defence against some fungal and bacterial nonhost pathogens entering by direct penetration 1-4 . In above-ground organs, PEN3 is recruited to sites of pathogen attack at the cell surface 3,4 . In seedling roots, PEN3 polarly localizes to the epidermal outer membrane domain in the absence of pathogens 5,6 . Root epidermal cells display four major polar plasma membrane domains: the outer domain facing the environment, the inner domain oriented towards the cortical cell layer, the shootward-oriented, apical, and the root tip-oriented, basal, domain 6 . Proteins in the outer domain that function in regulating the transport of inorganic compounds include, for example, the NIP5;1 boric acid uptake channel 7 . Factors required for PEN3 and NIP5;1 trafficking from the transGolgi network to the outer domain have been identified [8][9][10] , and exocyst complex components promote polar tethering of several outer domain proteins 9,11 . However, factors that specifically mediate trafficking of polar outer membrane cargos involved in responses to root-penetrating pathogens remain to be discovered.In a genetic screen for mislocalization of PEN3 fused to greenfluorescent protein (PEN3-GFP) in the root epidermis of seedlings 9 , we recovered one recessive mutant in which PEN3-GFP localized to a cytoplasmic structure resembling the endoplasmic reticulum (ER) (Fig. 1a-d). This er-arrested pen3-1 (eap3-1) mutation indistinguishably affected localization of PEN3-GFP from that of PEN3-mCherry ( Supplementary Fig. 1a,b), which colocalized with the ER-intrinsic chaperone BIP in the eap3-1 mutant ( Supplementary Fig. 1c,d), corroborating an ER arrest of PEN3.We mapped the eap3-1 mutation to a 275-kb interval on chromosome 3 by recombination mapping (Fig. 1e) combined with mapping and mutation identification by deep sequencing. This interval contained one non-synonymous, single-nucleotide polymorphism that caused a G to A missense mutation resulting in the conversion of glycine 192 to glutamate (eap3 G192E ) in the predicted open reading frame of gene model At3g09030.1 (Fig. 1f). Wild type and homozygous eap3-1 mutants displayed similar EAP3 transcript levels ( Fig. 1g), whereas the SALK_101331 T-DNA insertion located in the single exon of At3g09030 (designated eap3-2) caused a lack of full-length EAP3 messenger ...

ABCG36/PEN3/PDR8 Is an Exporter of the Auxin Precursor, Indole-3-Butyric Acid, and Involved in Auxin-Controlled Development

“…In summary, these data support a dual function of ABCG36 in the polar (rootward) distribution of IBA in the root and local IBA/IAA homeostasis in the very root tip. These features correlate with the mainly polar (lateral) expression pattern in the mature root and a widely non-polar expression in the LR cap cells (see Figure 3D; Strader and Bartel, 2009; Ruzicka et al, 2010; Mao et al, 2016, 2017).…”

A phospho-switch provided by LRR receptor-like kinase, ALK1/QSK1/KIN7, prioritizes ABCG36/PEN3/PDR8 transport toward defense

“…At first, we tested an elicitor prepared from Fusarium oxysporum (Fo), a well-characterized, ubiquitous root vascular fungal pathogen that causes wilt disease on several plant species, including Arabidopsis thaliana (Gordon, 2017). Moreover, we had previously shown that agcg36/pen3 is hypersensitive to Fo infection (Mao et al, 2017b). Like IBA and CLX, Fo elicitor treatment resulted in strong accumulation of ABCG36 but not that of ALK1 (Fig.…”

Plant Cells under Attack: Unconventional Endomembrane Trafficking during Plant Defense

“…The myrosinase PEN2 and the ABC-transporter PEN3 mediate callose deposition as well, and furthermore control the production (PEN2) and secretion (PEN3) of Trp-derived antimicrobial glucosinolates [46,47]. Both pathways require rather complex activation mechanisms [48,49] but eventually lead to the rapid relocalization of intracellular PEN1 and PEN3 pools to the PM [31]. As both PEN1 and PEN3 participate in fusion processes at the PM during both abiotic and biotic stresses [49], it is still unclear how exactly pathogens manipulate these pathways.…”

“…Both pathways require rather complex activation mechanisms [48,49] but eventually lead to the rapid relocalization of intracellular PEN1 and PEN3 pools to the PM [31]. As both PEN1 and PEN3 participate in fusion processes at the PM during both abiotic and biotic stresses [49], it is still unclear how exactly pathogens manipulate these pathways. One possibility is that the interaction of the B. graminis effector BEC4 with the ARF-GAP AGD5 and an ubiquitin-conjugating enzyme results in degradation of AGD5 [50].…”