Modulation of plant defense responses to herbivores by simultaneous recognition of different herbivore-associated elicitors in rice

Abstract

Induced plant defense responses against insect herbivores are triggered by wounding and/or perception of herbivore elicitors from their oral secretions (OS) and/or saliva. In this study, we analyzed OS isolated from two rice chewing herbivores, Mythimna loreyi and Parnara guttata. Both types of crude OS had substantial elicitor activity in rice cell system that allowed rapid detection of early and late defense responses, i.e. accumulation of reactive oxygen species (ROS) and defense secondary metabolites, respectively. While the OS from M. loreyi contained large amounts of previously reported insect elicitors, fatty acid-amino acid conjugates (FACs), the elicitor-active P. guttata’s OS contained no detectable FACs. Subsequently, elicitor activity associated with the high molecular mass fraction in OS of both herbivores was identified, and shown to promote ROS and metabolite accumulations in rice cells. Notably, the application of N-linolenoyl-Gln (FAC) alone had only negligible elicitor activity in rice cells; however, the activity of isolated elicitor fraction was substantially promoted by this FAC. Our results reveal that plants integrate various independent signals associated with their insect attackers to modulate their defense responses and reach maximal fitness in nature.

The effects of Lepidopteran oral secretion on plant wounds: A case study on the interaction between <i>Spodoptera litura</i> and <i>Arabidopsis thaliana</i>

“…However, S. litura OS treated leaves displayed more pronounced YFP signals than controls ( Figure 1B). This observation confirms previous findings that herbivore stress activates more intense JA defense responses than by wounding alone (Shinya et al 2016). …”

Integration of danger peptide signals with herbivore‐associated molecular pattern signaling amplifies anti‐herbivore defense responses in rice

“…Compared with mock‐treated controls, all tested OsPeps promoted the accumulation of reactive oxygen species (ROS) (Figures b and S1a) and also that of p ‐coumaroylputrescine (CoP), which is a well‐characterized herbivory‐induced secondary metabolite in rice (Alamgir et al ., ) (Figures c and S1b). While the application of OsPep consistently triggered accumulation of CoP it did not significantly increase levels of momilactone B (MB), a typical diterpene phytoalexin of rice previously shown to be weakly induced by herbivory (Figures c and S1b) (Alamgir et al ., ; Shinya et al ., ). This was in contrast to the fungal elicitor (GlcNAc) 8 which strongly induced both CoP and MB in cultured rice cells.…”

“…Under such circumstances, and despite some limitations resulting from cultivation in the presence of the growth hormone 2,4‐dichlorophenoxyacetic acid (2,4‐D), rice cell culture systems can be used as an alternative approach. In particular, such a system allows direct application of the desired elicitors to the cells (Shinya et al ., ), and this was considered a major advantage of the current study.…”

“…Following the perception of HAMPs and DAMPs by their cognate receptors, triggered signals are thought to be integrated in order to attain highly effective defense responses (Schmelz et al ., ; Schmelz, ; Duran‐Flores and Heil, ). Consistent with this, defense amplification was recently reported when two coexisting HAMPs in Mythimna loreyi (MYL) OS, fatty acid‐amino acid conjugates (FACs) and a high molecular elicitor (HME) fraction, were simultaneously applied to plant cells (Shinya et al ., ). This finding not only shows an example of interactions between HAMP signaling pathways but also implies that HAMP signaling may interact with other wound (or herbivory) associated signals, such as DAMPs, in tailoring plant defense against herbivores.…”

Differential induction of volatiles in rice plants by two stink bug species influence behaviour of conspecifics and their natural enemy Telenomus podisi

“…The response of a plant to herbivory depends on various factors, such as the ability to recognize the chemical elicitors in the saliva of the insect, and the type of feeding injury (Bonaventure, 2012;Shinya et al, 2016). The PCA indicated that the sesquiterpenes were related to the chemical profile of T. limbativentris-damaged plants.…”