Untitled

Abstract

The Gns1 gene of rice (Oryza sativa L. japonica) encodes 1,3;1,4-beta glucanase (EC 3.2.1.73), which hydrolyzes 1,3;1,4-beta-glucosidic linkages on 1,3;1,4-beta-glucan, an important component of cell walls in the Poaceae family. RNA and protein gel blot analyses demonstrated that blast disease or dark treatment induced the expression of the Gns1 gene. To assess the function of the Gns1 gene in disease resistance, we characterized transgenic rice plants constitutively expressing the Gns1 gene. The introduced Gns1 gene was driven by the CaMV 35S promoter and its products were found in the apoplast and accumulated in up to 0.1% of total soluble protein in leaves. Although transgenic plants showed stunted growth and impaired root formation, fertility, germination, and coleoptile elongation appeared unaffected compared to non-transgenic control plants, indicating that Gns1 does not play a crucial role in rice germination and coleoptile elongation. When transgenic plants were inoculated with virulent blast fungus (Magnaporthe grisea), they developed many resistant-type lesions on the inoculated leaf accompanying earlier activation of defense-related genes PR-1 and PBZ1 than in control plants. Transgenic plants spontaneously produced brown specks, similar in appearance to those reported for an initiation type of disease-lesion-mimic mutants, on the third and fourth leaves and occasionally on older leaves without inoculation of pathogens. Expression of the two defense-related genes was drastically increased after the emergence of the lesion-mimic phenotype.

Expression of pathogenesis-related proteins in transplastomic tobacco plants confers resistance to filamentous pathogens under field trials

“…Several strategies have been evaluated to obtain disease resistant crops through genetic engineering of the nuclear genome, including overexpression of PR proteins coding genes (for a review see 17,29 ). Although constitutive expression of PR proteins has been considered a promising strategy, limitations were observed, including low expression levels and the appearance of lesion mimic phenotypes 32,33 , have made it non-viable from a breeding perspective. In order to evaluate if tobacco PR proteins AP24 and β-1,3-glucanase can provide protection against filamentous pathogens without any associated undesired phenotypes when expressed from the plastid genome, we took advantage of plastid genome transformation of tobacco plants.…”

“…However, in many cases the levels of associated resistance were insufficient for breeding purposes 25,30 . Moreover, constitutive expression of PR proteins can result in a lesion mimic phenotype (i.e., the spontaneous formation of lesions resembling HR lesions in the absence of a pathogen) that can arise as an undesirable consequence 31–33 . In order to be adopted by farmers, strategies to deploy disease resistance, should be able to control specific diseases without affecting crops yield or quality 34 .…”

Proteomic analysis of pathogen‐responsive proteins from rice leaves induced by rice blast fungus,Magnaporthe grisea

“…However, there is little information available on the biochemical or physiological roles of these genes and/or their induction in response to pathogen attack. Recently, it was reported that a transgenic plant harboring the rice b-1,3 GIu gene (Gns1) showed a lesion mimic phenotype and exhibited enhanced resistance against the rice blast fungus [22]. However, based on 2-DE and Northern blot analyses, we are the first to show that two acidic and basic rice b-1,3 GIu are constantly induced both in the resistance and susceptible response against rice blast fungus attack.…”

A rice β-1,3-glucanase gene Osg1 is required for callose degradation in pollen development

“…Bars 10 m. Anthers at the premeiosis (a, e), early meiosis (b, f), later meiosis (c, g), tetrad (d, h), early microspore (i, m), later microspore (j, n), pollen mitosis (k, o), and mature pollen stages (l, p) in plant defense and development (Romero et al 1998;Akiyama and Pillai 2001;Akiyama et al 2004Akiyama et al , 2009). In addition, Gns1-over-expressing transgenic plants have been found to display a lesion mimic phenotype and exhibit enhanced resistance to rice blast fungus (Nishizawa et al 2003). Osg1 is classiWed into subfamily A which includes -1,3-glucanases involved in protection against fungi (Yamaguchi et al 2002).…”

“…Gns1 expression is regulated by ethylene, cytokinin, wounding, salicylic acid, and fungal elicitors (Simmons et al 1992). Gns1-over-expressing plants exhibit signiWcantly higher resistance to rice blast than WT plants (Nishizawa et al 2003). Two other rice endo-(1,3;1,4)--glucanase genes, denoted OsEGL1 and OsEGL2, have been isolated subsequently (Akiyama et al 2009).…”