Identification of transcription factors affecting CrPR1a induction in periwinkle and their potential roles in plant defense against phytoplasma
J. CHEN (1), H. Lo (2), C. Lai (2), C. Lin (2) (1) Institute of Biotechnology/National Taiwan University, Taiwan; (2) Department of Plant Pathology & Microbiology/National Taiwan University, Taiwan

Phytoplasma, a wall-less obligate bacterial pathogen, is associated with more than a thousand plant diseases and causes huge economic losses. After infection, phytoplasmas are restricted inside phloem but can induce serious systemic symptoms on plant. For example, periwinkle leaf yellowing phytoplasma (PLY) can cause symptoms of leaf yellowing, phyllody, and witches’-broom on periwinkle (Catharanthus roseus). After PLY infection, CrPR1a is strongly induced through salicylic acid-related defense pathway, and silencing of CrNPR1 using the VIGS technique resulted in reduced induction of CrPR1a, and accelerated symptom development after phytoplasma infection. To further identify transcription factors that affect CrPR1a expression after pathogen infection, a virus-induced gene silencing (VIGS)-based screening was conducted. After screening of 329 factors that belong to groups related with stress responses, 3 auxin response factors (ARF), 1 Aux/IAA, and 1 bZIP were identified. Because ARF and Aux/IAA are reported to participate in auxin signaling, it is very possible that auxin affects plant defense and results in reduced induction of CrPR1a. Indeed, exogenous auxin treatment accelerates symptom progression of PLY-infected periwinkles, and suppresses induction of CrPR1a. Our results indicate the potential interplays of phytohormones in plant defense against phytoplamsas.

Abstract Number: P16-443
Session Type: Poster