Characterizing Rice Lesion Mimic Mutants and Identifying a Mutant with Broad-Spectrum Resistance to Rice Blast and Bacterial Blight

Abstract

Many plant mutants develop spontaneous lesions that resemble disease symptoms in the absence of pathogen attack. In several pathosystems, lesion mimic mutations have been shown to be involved in programmed cell death, which in some instances leads to enhanced disease resistance to multiple pathogens. We investigated the relationship between spontaneous cell death and disease resistance in rice with nine mutants with a range of lesion mimic phenotypes. All nine mutations are controlled by recessive genes and some of these mutants have stunted growth and other abnormal characteristics. The lesion mimics that appeared on the leaves of these mutants were caused by cell death as measured by trypan blue staining. Activation of six defense-related genes was observed in most of the mutants when the mimic lesions developed. Four mutants exhibited significant enhanced resistance to rice blast. One of the mutants, spl11, confers non-race-specific resistance not only to blast but also to bacterial blight. The level of resistance in the spl11 mutant to the two pathogens correlates with the defense-related gene expression and lesion development on the leaves. The results suggest that some lesion mimic mutations in rice may be involved in disease resistance, and cloning of these genes may provide a clue to developing broad-spectrum resistance to diverse pathogens.

Arabidopsis Cell Death in Compatible and Incompatible Interactions with Alternaria brassicicola

“…Phenotypically, cell death is a prerequisite in the compatible interaction between Arabidopsis and A. brassicicola. Lesion mimic mutants, such as barley mlo, show a broad-spectrum disease resistance against biotrophic pathogens but are highly susceptible to necrotrophic pathogens (Aviv et al, 2002;Huckelhoven et al, 2001;Jarosch et al, 2003;Salmeron and Vernooij, 1998;Yao et al, 2009;Yin et al, 2000). This ambivalence further supports the opposing contribution of PCD to the interaction.…”

Ubiquitination-mediated protein degradation and modification: an emerging theme in plant-microbe interactions

“…The spl11 mutant conferred elevated non-race-specific resistance to both M. grisea and Xanthomonas oryzae pv. oryzae, the causal pathogens of rice blast and bacterial blight diseases, respectively [80]. The enhanced resistance of the spl11 mutant to the two pathogens correlates with the constitutive expression of several defense-related genes and lesion development on Ubiquitination-mediated protein degradation in plant-microbe interactions 420 npg the leaves [80].…”

“…oryzae, the causal pathogens of rice blast and bacterial blight diseases, respectively [80]. The enhanced resistance of the spl11 mutant to the two pathogens correlates with the constitutive expression of several defense-related genes and lesion development on Ubiquitination-mediated protein degradation in plant-microbe interactions 420 npg the leaves [80]. The constitutive activation of defense responses in the spl11 mutant was further confirmed when an array-based expression profiling was performed using the Sygenta rice gene chips that harbor nearly half of all rice genes [81] to analyze the impact of the spl11 mutation on the rice transcriptome.…”

Interactions between theS-Domain Receptor Kinases and AtPUB-ARM E3 Ubiquitin Ligases Suggest a Conserved Signaling Pathway in Arabidopsis

“…A strong connection to plant defense responses is emerging for several PUB-ARM proteins. The rice SPL11 gene was identified in a genetic screen for lesion mimic mutants (Yin et al, 2000), and the spl11 mutant displays spontaneous lesions and enhance resistance to fungal and bacterial pathogens implicating SPL11 as a negative regulator of cell death (Zeng et al, 2004). In contrast, the Arabidopsis PUB17 protein and the orthologous tobacco (Nicotiana tabacum) ACRE276 protein appear to be positive regulators of cell death and defense responses because RNAi and knockout plants are compromised in these responses .…”