A Pleiotropic Drug Resistance Transporter TaABCG36 Contributes to Defense against <i>Puccinia triticina</i> in <i>Triticum aestivum</i>

ABC transporters play important roles in plant growth and resistance to abiotic and biotic stresses. Here, we showed that the TaABCG36 gene positively regulates leaf rust resistance in the wheat line Thatcher + Lr19 (TcLr19) when challenged with an avirulent pathotype of Puccinia triticina (Pt). The TaABCG36 gene was cloned from genomic DNA and cDNA from wheat line TcLr19. The clone was 6730 bp in gDNA and 4365 bp in cDNA for this gene. It encoded an ABC transporter with 1454 amino acids in length. BLASTp analysis indicated a considerable identity ABC transporter G family member 36 with Aegilops tauschii subsp. strangulata, Triticum dicoccoides, and T. aestivum; thus, we named the gene TaABCG36. TaABCG36 was proved to be a plasma transmembrane protein by bioinformatic analysis and subcellular localization of the TaABCG36–GFP fusion protein. The expression of TaABCG36 in wheat leaves reached a peak at 72 h post-inoculation by Pt avirulence pathotype, and the expression was also induced by phytohormone treatments of salicylic acid (SA), abscisic acid (ABA), and methyl jasmonate (MeJA). Three fragments (V1–V3) of the TaABCG36 gene were introduced to the BSMV-VIGS vector and, thus, silenced the expression of TaABCG36 in the wheat line TcLr19. All the three BSMV:VIGS-infected plants showed reaction type “3” to Pt pathotype THTS, which was fully avirulent on TcLr19 (infection type “0”). Histopathological observation showed that silencing of TaABCG36 facilitated the formation of haustorial mother cells (HMC) and mycelial growth, implying that TaABCG36 plays a positive role in the response of TcLr19 against THTS. These results provide molecular insight into the interaction between Pt and its wheat host and identify a potential target for engineering resistance in wheat to damaging pathogen of Pt