Submergence deactivates wound-induced plant defence against herbivores

Hyo-Jun Lee,Jae Heung Jeon,Hye Sun Cho,Sang-Gyu Kim,Gisuk Lee,Ji-Sun Park,Seung Yong Shin,Hyun-Soon Kim

doi:10.1038/s42003-020-01376-4

Abstract

Flooding is a common and critical disaster in agriculture, because it causes defects in plant growth and even crop loss. An increase in herbivore populations is often observed after floods, which leads to additional damage to the plants. Although molecular mechanisms underlying the plant responses to flooding have been identified, how plant defence systems are affected by flooding remains poorly understood. Herein, we show that submergence deactivates wound-induced defence against herbivore attack in Arabidopsis thaliana. Submergence rapidly suppressed the wound-induced expression of jasmonic acid (JA) biosynthesis genes, resulting in reduced JA accumulation. While plants exposed to hypoxia in argon gas exhibited similar reduced wound responses, the inhibitory effects were initiated after short-term submergence without signs for lack of oxygen. Instead, expression of ethylene-responsive genes was increased after short-term submergence. Blocking ethylene signalling by ein2-1 mutation partially restored suppressed expression of several wound-responsive genes by submergence. In addition, submergence rapidly removed active markers of histone modifications at a gene locus involved in JA biosynthesis. Our findings suggest that submergence inactivates defence systems of plants, which would explain the proliferation of herbivores after flooding.

Highlights

Flooding is a common and critical disaster in agriculture, because it causes defects in plant growth and even crop loss
Whereas the expression levels of JAZ7, JAZ10, and OPR3 were significantly elevated after wounding in the air (JAZ7, P = 0.00005, Hedges′ g = 5.80; JAZ10, P = 0.000005, Hedges′ g = 7.63; OPR3, P < 1.0 × 10−7, Hedges′ g = 14.4), the induction was largely suppressed when wounding was done in water (Fig. 1a)
We examined the promoter activity of JAZ10 gene using pJAZ10:GUS seedlings; the results showed that woundinduced GUS expression was largely down-regulated after submergence (Fig. 1d)

Summary

Introduction

Flooding is a common and critical disaster in agriculture, because it causes defects in plant growth and even crop loss. An increase in herbivore populations is often observed after floods, which leads to additional damage to the plants. Submergence rapidly suppressed the wound-induced expression of jasmonic acid (JA) biosynthesis genes, resulting in reduced JA accumulation. While plants exposed to hypoxia in argon gas exhibited similar reduced wound responses, the inhibitory effects were initiated after short-term submergence without signs for lack of oxygen. Expression of ethylene-responsive genes was increased after short-term submergence. In addition to hypoxiainduced plant damage, outbreak of herbivores is another phenomenon observed after flooding. Both continuous and periodic flooding trigger an increase in herbivore populations in rice[4]. The effects of flooding on plant defence responses to herbivore attack remain largely unknown. The expression of genes involved in JA biosynthesis, including those encoding LIPOXYGENASE (LOX), ALLENE OXIDE SYNTHASE (AOS), ALLENE OXIDE

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Conclusion