| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 2014: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2013: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2012: ¥600,000 (Direct Cost: ¥600,000)
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| Outline of Annual Research Achievements |
In Africa, the most economically important constraints to crop production include Striga species i. e., S. hermonthica and S. asiatica, among others, which affect the production of sorghum, millet, maize, sugarcane and cowpea resulting in losses of up to USD 1 billion annually affecting over 100 million farmers. The fundamental strategies to control Striga are to prevent their reproduction, to destroy their soil seed bank and to limit their spread to new uninfested areas. Towards this end, cultivars and wild relatives of several crop species including sorghum, which show resistance to Striga have been identified. In rice, it was found that Nipponbare, a japonica cultivar is resistant against Striga. However, the molecular mechanisms underlying resistance are not well understood. In our study, we conducted an in-depth characterization of the roles of SA and JA in rice defence against Striga hermonthica. We found out that jasmonic acid (JA) and salicylic acid (SA) defence pathways were i
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nduced in rice roots after infection. Using JA and SA pathway mutants, we found that inhibiting JA biosynthesis resulted in severe Striga susceptibility only recovered by treating plants with JA. On the other hand, SA-deficient rice were resistant against Striga. The resistance phenotype was characterized by a strong induction of the JA defence pathway. In the Striga-infected rice roots, we found that a gene called OsWRKY45 was highly expressed. When we knocked down this gene, the plants were highly susceptible to Striga infection and the susceptibility was recovered by addition of JA. These results highlighted the significance of OsWRKY45 in regulating both the JA and SA defence pathways in resistance against Striga parasitism. These data offer to our knowledge, the first insight into the resistance mechanisms that enable monocots to resist Striga parasitism and have revealed several previously unknown characteristics of defence pathway crosstalk. Knowledge of the mechanisms involved in the complex JA and SA interactions are necessary to understand the evolution of resistance and the development of successful solutions to parasitic weed problems in agriculture. Less
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