Abstract
Plant hormones have a prominent place in the plant immune and defense mechanism. To gain more information about the plant hormone pathways involved in rice defense against nematodes, here, we studied the roles of three core hormones, namely, salicylic acid (SA), jasmonate (JA), and ethylene (ET) in rice defense to Aphelenchoides besseyi by using the susceptible variety, Nipponbare as well as the resistant variety Tetep. The data showed that Tetep exhibited pre- and post-invasion with suppression of nematode infection, development, and reproduction. The quantitative real-time (qRT)-PCR analysis of plant hormone marker genes in the two cultivars clearly revealed that all the SA-related genes were downregulated in susceptible Nipponbare plants but were significantly upregulated in resistant Tetep plants at the flowering stage. The exogenous application of the SA analog, benzo-1,2,3-thiadiazole-7-carbothioic acid S-methyl ester (BTH), methyl jasmonate (MeJA), and ethephon did induce rice resistance to A. besseyi, and the rice plants treated by hormone inhibitors increased susceptibility to A. besseyi. Similarly, corresponding transgenic biosynthesis or signaling mutants of those hormones also showed an increased susceptibility. Collectively, these results suggest that SA, JA, and ET play important defense roles in rice against A. besseyi.
Highlights
Rice (Oryza sativa) is a major food source that feeds more than one-third of the world population
It has been reported that Tetep is highly resistant to A. besseyi according to the few nematodes in 100 grains and the lack of “white tip” symptom, but the underlying mechanism remains largely unknown (Feng et al, 2014)
To gain insights into the defense mechanisms of Tetep against A. besseyi, in this study, the number of nematodes and the expression levels of plant hormone marker genes were investigated in cultivar Tetep and Nipponbare
Summary
Rice (Oryza sativa) is a major food source that feeds more than one-third of the world population. During the growth of rice plants, they are potential targets for more than 100 species of plant parasitic nematodes (Fortuner and Merny, 1979); Aphelenchoides besseyi, known as the rice white tip nematode, is one of the most important parasitic nematodes of rice (Duncan and Moens, 2013). As a seed-borne nematode, A. besseyi can survive on stored grain in anhydrobiosis for several years (Tiwari and Khare, 2003). Anabiotic A. besseyi rapidly become active and are attracted to rice meristematic areas. The nematodes migrate in the leaf or young tissue of rice as ecto- and endoparasites and cause a typical symptom of whitening and withering at the leaf tips (Togashi and Hoshino, 2001; Duncan and Moens, 2013). A. besseyi can be found in low numbers at all green
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