**Rice** *OsAAA-ATPase1* **is Induced during Blast Infection in a Salicylic Acid-Dependent Manner, and Promotes Blast Fungus Resistance**

**Xinqiong Liu 1,\*,**†**, Haruhiko Inoue 2,**†**, Xianying Tang 1, Yanping Tan 1, Xin Xu 1, Chuntai Wang <sup>1</sup> and Chang-Jie Jiang 2,\***


Received: 29 January 2020; Accepted: 18 February 2020; Published: 20 February 2020

**Abstract:** Fatty acids (FAs) have been implicated in signaling roles in plant defense responses. We previously reported that mutation or RNAi-knockdown (*OsSSI2*-kd) of the rice *OsSSI2* gene, encoding ta stearoyl acyl carrier protein FA desaturase (SACPD), remarkably enhanced resistance to blast fungus *Magnaporthe oryzae* and the leaf-blight bacterium *Xanthomonas oryzae* pv. *oryzae* (*Xoo*). Transcriptomic analysis identified six AAA-ATPase family genes (hereafter *OsAAA-ATPase1–6*) upregulated in the *OsSSI2*-kd plants, in addition to other well-known defense-related genes. Here, we report the functional analysis of *OsAAA-ATPase1* in rice's defense response to *M. oryzae*. Recombinant OsAAA-ATPase1 synthesized in *Escherichia coli* showed ATPase activity. *OsAAA-ATPase1* transcription was induced by exogenous treatment with a functional analogue of salicylic acid (SA), benzothiadiazole (BTH), but not by other plant hormones tested. The transcription of *OsAAA-ATPase1* was also highly induced in response to *M. oryzae* infection in an SA-dependent manner, as gene induction was significantly attenuated in a transgenic rice line expressing a bacterial gene (*nahG*) encoding salicylate hydroxylase. Overexpression of *OsAAA-ATPase1* significantly enhanced pathogenesis-related gene expression and the resistance to *M. oryzae*; conversely, RNAi-mediated suppression of this gene compromised this resistance. These results suggest that *OsAAA-APTase1* plays an important role in SA-mediated defense responses against blast fungus *M. oryzae*.

**Keywords:** AAA-ATPase; salicylic acid; fatty acid; rice; *Magnaporthe oryzae*; disease resistance
