Herbivore-Induced Callose Deposition on the Sieve Plates of Rice: An Important Mechanism for Host Resistance    

Abstract

The brown planthopper (Nilaparvata lugens Stål; BPH) is a specialist herbivore on rice (Oryza sativa) that ingests phloem sap from the plant through its stylet mouthparts. Electronic penetration graphs revealed that BPH insects spent more time wandering over plants carrying the resistance genes Bph14 and Bph15, but less time ingesting phloem than they did on susceptible plants. They also showed that their feeding was frequently interrupted. Tests with [ 14 C]sucrose showed that insects ingested much less phloem sap from the resistant than the susceptible plants. BPH feeding up-regulated callose synthase genes and induced callose deposition in the sieve tubes at the point where the stylet was inserted. The compact callose remained intact in the resistant plants, but genes encoding b-1,3-glucanases were activated, causing unplugging of the sieve tube occlusions in susceptible plants. Continuing ingestion led to a remarkable reduction in the susceptible plants' sucrose content and activation of the RAmy3D gene, leading to starch hydrolysis and ultimately carbohydrate deprivation in the plants. Our results demonstrate that BPH feeding induces the deposition of callose on sieve plates in rice and that this is an important defense mechanism that prevents insects from ingesting phloem sap. In response, however, the BPH can unplug sieve tube occlusions by activating b-1,3-glucanase genes in rice plants.

Transcriptomics of induced defense responses to greenbug aphid feeding in near isogenic wheat lines

“…Studies have reported that plants up-regulate callose synthase, β-1,3-glucanase, and polygalacturonase in response to herbivore attack, which are also found in insect saliva [23,32].…”

“…Infestation by brown plant hopper (Nilaparvata lugens Stal; BPH), a phloem feeder in rice resulted in increased callose deposition at the site of stylet penetration in sieve tubes coupled with up-regulation of transcripts encoding β-1,3-glucanases to unplug sieve tube occlusion [32]. The expression patterns of β-1,3-glucanase genes in BPH susceptible plants following infestation was much higher compared to plants carrying two resistant genes, one of them is a potential R gene [14,32]. Our results agree with these findings where SB showed increased expression of three β-1,3-glucanase related transcripts at 24 and 48 hai (Fig.…”

“…Additionally, as part of the defense mechanisms against phloem-feeding insects and other herbivores, plants are known to alter secondary metabolites, glutathione S-transferases (GSTs), peroxidases, and redox homeostasis [19,[29][30][31]. As a defensive mechanism, plants resistant to phloem feeding herbivores increase callose deposition in sieve tubes; while susceptible plants promote callose-decomposing enzymes such as β-1,3-glucanase (also present in aphid saliva), resulting in unplugging of phloem occlusion [32].…”

Callose Synthase GSL7 Is Necessary for Normal Phloem Transport and Inflorescence Growth in Arabidopsis

“…If mature phloem elements are damaged, massive callose synthesis occurs on the sieve plate, resulting in occlusion of the pores and retention of phloem contents behind the callose plugs (Evert and Derr, 1964;Hao et al, 2008;Mullendore et al, 2010). Indeed, because callose is formed very rapidly upon damage to the phloem, its existence in sieve plate pores in undamaged plants has been disputed in the past: some authors have argued that its presence is an artifact of sectioning and preparation techniques (Evert and Derr, 1964;Walsh and Melaragno, 1976;Spanner, 1978;Sjö lund, 1997; for summary, see van Bel, 2003).…”

Deciphering the Responses of Root Border-Like Cells of Arabidopsis and Flax to Pathogen-Derived Elicitors

“…The recognition of MAMPs through specific plant receptors triggers the activation of a collaborative defense response to restrict pathogen growth. This primary innate immune response includes the induction of mitogen-activated protein kinase signaling, transcriptional reprogramming, production of reactive oxygen species (ROS; Boller and Felix, 2009;Millet et al, 2010), and modifications of cell wall structure via deposition of callose (Hao et al, 2008) or accumulation of Hyp-rich glycoproteins such as extensin (Wojtaszek et al, 1995;Ribeiro et al, 2006). Most of this knowledge has come from a number of studies performed on leaves.…”