Stein Mónica, Dittgen Jan, Sánchez-Rodríguez Clara, Hou Bi-Huei, Molina Antonio, Schulze-Lefert Paul, Lipka Volker, Somerville Shauna
Carnegie Institution, Department of Plant Biology, Stanford, California, 94305, USA.
Plant Cell. 2006 Mar;18(3):731-46. doi: 10.1105/tpc.105.038372. Epub 2006 Feb 10.
Arabidopsis thaliana is a host to the powdery mildew Erysiphe cichoracearum and nonhost to Blumeria graminis f. sp hordei, the powdery mildew pathogenic on barley (Hordeum vulgare). Screening for Arabidopsis mutants deficient in resistance to barley powdery mildew identified PENETRATION3 (PEN3). pen3 plants permitted both increased invasion into epidermal cells and initiation of hyphae by B. g. hordei, suggesting that PEN3 contributes to defenses at the cell wall and intracellularly. pen3 mutants were compromised in resistance to the necrotroph Plectosphaerella cucumerina and to two additional inappropriate biotrophs, pea powdery mildew (Erysiphe pisi) and potato late blight (Phytophthora infestans). Unexpectedly, pen3 mutants were resistant to E. cichoracearum. This resistance was salicylic acid-dependent and correlated with chlorotic patches. Consistent with this observation, salicylic acid pathway genes were hyperinduced in pen3 relative to the wild type. The phenotypes conferred by pen3 result from the loss of function of PLEIOTROPIC DRUG RESISTANCE8 (PDR8), a highly expressed putative ATP binding cassette transporter. PEN3/PDR8 tagged with green fluorescent protein localized to the plasma membrane in uninfected cells. In infected leaves, the protein concentrated at infection sites. PEN3/PDR8 may be involved in exporting toxic materials to attempted invasion sites, and intracellular accumulation of these toxins in pen3 may secondarily activate the salicylic acid pathway.
拟南芥是白粉菌菊科白粉菌的寄主，对大麦白粉菌（禾本科布氏白粉菌大麦专化型，寄生于大麦（Hordeum vulgare）上的白粉菌）是非寄主。对拟南芥中对大麦白粉菌抗性缺陷的突变体进行筛选，鉴定出了渗透3（PEN3）。pen3植株允许禾本科布氏白粉菌大麦专化型对表皮细胞的侵入增加以及菌丝的起始，这表明PEN3有助于细胞壁和细胞内的防御。pen3突变体对坏死营养型黄瓜盘长孢以及另外两种不相宜的活体营养型病原菌——豌豆白粉菌（豌豆白粉菌）和马铃薯晚疫病（致病疫霉）的抗性受损。出乎意料的是，pen3突变体对菊科白粉菌具有抗性。这种抗性依赖水杨酸且与褪绿斑相关。与该观察结果一致，相对于野生型，水杨酸途径基因在pen3中被高度诱导。pen3所赋予的表型是由多效性药物抗性8（PDR）8功能丧失导致的，PDR8是一个高表达的假定ATP结合盒转运蛋白。用绿色荧光蛋白标记的PEN3/PDR8定位于未感染细胞的质膜。在受感染的叶片中，该蛋白集中在感染部位。PEN3/PDR8可能参与将有毒物质输出到试图侵入的部位，并且这些毒素在pen3中的细胞内积累可能继而激活水杨酸途径。
