https://www.cell.com/trends/immunology/pdf/S1471-4906(14)00094-5.pdf

Plant pattern-recognition receptors.

The plant basal immune system can detect broadly present microbe-associated molecular patterns (MAMPs, also called PAMPs) and induce defenses, but adapted microbes express a suite of effector proteins that often act to suppress these defenses. Plants have evolved other receptors (R proteins) that detect these pathogen effectors and activate strong defenses. Pathogens can subsequently alter or delete their recognized effectors to avoid defense elicitation, at risk of a fitness cost associated with loss of those effectors. Significant research progress is revealing, among other things, mechanisms of MAMP perception, the host defense processes and specific host proteins that pathogen effectors target, the mechanisms of R protein activation, and the ways in which pathogen effector suites and R genes evolve. These findings carry practical ramifications for resistance durability and for future resistance engineering. The present review uses numerous questions to help clarify what we know and to identify areas that are ripe for further investigation.

Elicitors, Effectors, and R Genes: The New Paradigm and a Lifetime Supply of Questions

From a global viewpoint, a number of challenges need to be met for sustainable rice production: (i) increasingly severe occurrence of insects and diseases and indiscriminate pesticide applications; (ii) high pressure for yield increase and overuse of fertilizers; (iii) water shortage and increasingly frequent occurrence of drought; and (iv) extensive cultivation in marginal lands. A combination of approaches based on the recent advances in genomic research has been formulated to address these challenges, with the long-term goal to develop rice cultivars referred to as Green Super Rice. On the premise of continued yield increase and quality improvement, Green Super Rice should possess resistances to multiple insects and diseases, high nutrient efficiency, and drought resistance, promising to greatly reduce the consumption of pesticides, chemical fertilizers, and water. Large efforts have been focused on identifying germplasms and discovering genes for resistance to diseases and insects, N- and P-use efficiency, drought resistance, grain quality, and yield. The approaches adopted include screening of germplasm collections and mutant libraries, gene discovery and identification, microarray analysis of differentially regulated genes under stressed conditions, and functional test of candidate genes by transgenic analysis. Genes for almost all of the traits have now been isolated in a global perspective and are gradually incorporated into genetic backgrounds of elite cultivars by molecular marker-assisted selection or transformation. It is anticipated that such strategies and efforts would eventually lead to the development of Green Super Rice.

https://www.pnas.org/content/pnas/104/42/16402.full.pdf

Strategies for developing Green Super Rice.

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(09)00014-6.pdf

Against the grain: safeguarding rice from rice blast disease

In mammals, cadmium is widely considered as a non-genotoxic carcinogen acting through a methylation-dependent epigenetic mechanism. Here, the effects of Cd treatment on the DNA methylation patten are examined together with its effect on chromatin reconfiguration in Posidonia oceanica. DNA methylation level and pattern were analysed in actively growing organs, under short- (6 h) and long- (2 d or 4 d) term and low (10 mM) and high (50 mM) doses of Cd, through a Methylation-Sensitive Amplification Polymorphism technique and an immunocytological approach, respectively. The expression of one member of the CHROMOMETHYLASE (CMT) family, a DNA methyltransferase, was also assessed by qRT-PCR. Nuclear chromatin ultrastructure was investigated by transmission electron microscopy. Cd treatment induced a DNA hypermethylation, as well as an up-regulation of CMT, indicating that de novo methylation did indeed occur. Moreover, a high dose of Cd led to a progressive heterochromatinization of interphase nuclei and apoptotic figures were also observed after long-term treatment. The data demonstrate that Cd perturbs the DNA methylation status through the involvement of a specific methyltransferase. Such changes are linked to nuclear chromatin reconfiguration likely to establish a new balance of expressed/repressed chromatin. Overall, the data show an epigenetic basis to the mechanism underlying Cd toxicity in plants.

/pdf/in-posidonia-oceanica-cadmium-induces-changes-in-dna-3cu7uj83mr.pdf

In Posidonia oceanica cadmium induces changes in DNA methylation and chromatin patterning

Rice blast, caused by the fungal pathogen Magnaporthe grisea, is one of the most devastating diseases in rice worldwide. The dominant resistance gene, Pi-d2 [previously named Pi-d(t)2], present in the rice variety Digu, confers gene-for-gene resistance to the Chinese blast strain, ZB15. Pi-d2 was previously mapped close to the centromere of chromosome 6. In this study, the Pi-d2 gene was isolated by a map-based cloning strategy. Pi-d2 encodes a receptor-like kinase protein with a predicted extracellular domain of a bulb-type mannose specific binding lectin (B-lectin) and an intracellular serine-threonine kinase domain. Pi-d2 is a single-copy gene that is constitutively expressed in the rice variety Digu. Transgenic plants carrying the Pi-d2 transgene confer race-specific resistance to the M. grisea strain, ZB15. The Pi-d2 protein is plasma membrane localized. A single amino acid difference at position 441 of Pi-d2 distinguishes resistant and susceptible alleles of rice blast resistance gene Pi-d2. Because of its novel extracellular domain, Pi-d2 represents a new class of plant resistance genes.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-313X.2006.02739.x

De-xi Chen

Papers

A B-lectin receptor kinase gene conferring rice blast resistance.

Rice Blast Resistance of Transgenic Rice Plants with Pi-d2 Gene

Genetic Transformation of Rice with Pi-d2 Gene Enhances Resistance to Rice Blast Fungus Magnaporthe oryzae

Genetic Analysis of Streaked and Abnormal Floret Mutant st-fon