AUTHOR=Wang Zheng , Bao Ling-Li , Zhao Feng-Yun , Tang Min-Qiang , Chen Ting , Li Yaoming , Wang Bing-Xu , Fu Benzhong , Fang Hedi , Li Guan-Ying , Cao Jun , Ding Li-Na , Zhu Ke-Ming , Liu Sheng-Yi , Tan Xiao-Li 

TITLE=BnaMPK3 Is a Key Regulator of Defense Responses to the Devastating Plant Pathogen Sclerotinia sclerotiorum in Oilseed Rape

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00091

DOI=10.3389/fpls.2019.00091

ISSN=1664-462X

ABSTRACT=<p>The disease caused by <italic>Sclerotinia sclerotiorum</italic> has traditionally been difficult to control, resulting in tremendous economic losses in oilseed rape (<italic>Brassica napus</italic>). Identification of important genes in the defense responses is critical for molecular breeding, an important strategy for controlling the disease. Here, we report that a <italic>B. napus</italic> mitogen-activated protein kinase gene, <italic>BnaMPK3</italic>, plays an important role in the defense against <italic>S. sclerotiorum</italic> in oilseed rape. <italic>BnaMPK3</italic> is highly expressed in the stems, flowers and leaves, and its product is localized in the nucleus. Furthermore, <italic>BnaMPK3</italic> is highly responsive to infection by <italic>S. sclerotiorum</italic> and treatment with jasmonic acid (JA) or the biosynthesis precursor of ethylene (ET), but not to treatment with salicylic acid (SA) or abscisic acid. Moreover, overexpression (OE) of <italic>BnaMPK3</italic> in <italic>B. napus</italic> and <italic>Nicotiana benthamiana</italic> results in significantly enhanced resistance to <italic>S. sclerotiorum</italic>, whereas resistance is diminished in RNAi transgenic plants. After <italic>S. sclerotiorum</italic> infection, defense responses associated with ET, JA, and SA signaling are intensified in the <italic>BnaMPK3</italic>-OE plants but weakened in the <italic>BnaMPK3</italic>-RNAi plants when compared to those in the wild type plants; by contrast the level of both H<sub>2</sub>O<sub>2</sub> accumulation and cell death exhibits a reverse pattern. The candidate gene association analyses show that the BnaMPK3-encoding <italic>BnaA06g18440D</italic> locus is a cause of variation in the resistance to <italic>S. sclerotiorum</italic> in natural <italic>B. napus</italic> population. These results suggest that <italic>BnaMPK3</italic> is a key regulator of multiple defense responses to <italic>S. sclerotiorum</italic>, which may guide the resistance improvement of oilseed rape and related economic crops.</p>