Functional characterization of fatty acyl-coenzyme A reductase, RcFAR1, specially expressed by Rosa chinensis consequent to infection by rose powdery mildew, Podosphaera pannosa

Rose (Rosa chinensis), as the most popular cut flowers in the world, is perennially attacked by rose powdery mildew (Podosphaera pannosa) and beet armyworm (Spodoptera exigua). The indirect plant-mediated interactions between these two pests always exist in the ternary system consisting of these three organisms, but little is known about the molecular mechanisms for such interactions. In this paper, we investigated the function of an insect-resistance-related gene in rose, RcFAR1, encoding a fatty acyl coenzyme A reductase. The gene was expressed in the roses when the plants were infected by P. pannosa, and as a consequence, the resistance of the roses against S. exigua was significantly induced. The results from heterologous expression of RcFAR1 in Saccharomyces cerevisiae showed that RcFAR1 primarily accumulated primary alcohols, including C12:0, C16:0, and C18:0 by using GC-MS analyses. Overexpression in Arabidopsis thaliana resulted in 4.0-, 3.6-, 8.2-, and 3.1-fold increases in the contents of fatty alcohols in T1 generation plants of A. thaliana for C12:0, C14:0, C16:0, and C18:0, respectively, suggesting that RcFAR1 catalyzes the biosynthesis of primary alcohols of C12:0, C14:0, C16:0, and C18:0 in the plants. Transient expression in the tobacco showed that RcFAR1 localized to the cytoplasm or the cell membrane. Our study has elucidated the molecular mechanism for the synthesis of dodecanol, tetradecanol, hexadecanol and other primary alcohols in P. pannosa-infected roses, and thus revealed one of the important molecular regulatory mechanisms by which the resistances of the roses against S. exigua are induced by the infection of the roses by P. pannosa.