Ratoon rice generated from primed parent plants exhibit enhanced herbivore resistance

Authors: YE, MAO - South China Agricultural University; SONG, YUAN - South China Agricultural University; Baerson, Scott; LONG, JUN - South China Agricultural University; Pan, Zhiqiang - Peter; LIN, WEN - Fujian Agriculture And Forest University; ZENG, RENSEN - South China Agricultural University

Submitted to: Plant, Cell & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2016
Publication Date: 1/5/2017
Publication URL: https://handle.nal.usda.gov/10113/5801789
Citation: Ye, M., Song, Y., Baerson, S.R., Long, J., Pan, Z., Lin, W., Zeng, R. 2017. Ratoon rice generated from primed parent plants exhibit enhanced herbivore resistance. Plant, Cell & Environment. 40:779-789. doi:10.1111/poe.12897.

Interpretive Summary: Higher plants exhibit a type of physiological stress response frequently referred to as "priming memory", wherein they mount more rapid and robust defense responses against environmental challenges to which they have been previously exposed. This phenomenon has been documented for both abiotic stresses (e.g., drought, freezing), as well as biotic stresses such as exposure to insect herbivores, and may in some cases even be manifested for several generations. Biochemical and regulatory pathways associated with the production of allelochemicals and other defense compounds are also subject to the effects of priming memory, although the details surrounding the underlying mechanism for how this occurs is largely unknown. In this study, we demonstrate the ability of crops that can generate "ratoons", which are secondary crops generated directly from the existing shoots of original crop plants, to exhibit priming memory against insect herbivore infestation in ratoons derived from primary plants receiving prior insect exposures. In addition, we establish a link between the stress-associated plant hormone jasmonic acid (JA), which regulates plant responses to diverse stresses, and priming memory in rice ratoon plants. These findings have implications for agriculture, as primed defense responses would be anticipated to contribute to the improved adaptation of newly-generated ratoon crops.

Technical Abstract: Rice (Oryza sativa) plants have the ability to regenerate new panicle-bearing tillers post-harvest, and for this reason ratooning represents a practical approach for achieving increased production levels with limited labor input for this crop. Here we report that attack by insect herbivores, or treatment with a defense signaling compound during the vegetative stage of parent plants, can prime defense responses in subsequent ratoon plants without additional treatments or herbivore exposures. We compared the defense responses of rice ratoons generated from parent plants that had been either infested by Cnaphalocrocis medinalis (rice leaffolder, LF) caterpillars or treated with methyl jasmonate (MeJA) during vegetative growth, with ratoons generated from control parent plants. Ratoon plants generated from parents receiving prior LF infestation or MeJA treatment exhibited higher JA accumulation levels, as well as elevated levels of transcripts of defense-related genes associated with jasmonic acid (JA) signaling. In addition, elevated activity levels of peroxidase, polyphenol oxidase and trypsin protease inhibitor were observed, as well as enhanced resistance toward subsequent LF infestation. Pre-priming of ratoon defense responses was significantly reduced in plants where expression of OsAOS (allene oxide synthase, involved in JA biosynthesis) or OsCOI1 (CORONATINE INSENSITIVE1, involved in JA perception) was inhibited using RNA interference. Our results indicate that herbivore exposure or MeJA treatment in rice parent plants enhances resistance against herbivore infestation in subsequently-generated ratoons through priming of JA-mediated defenses.