In eukaryotes, ARGONAUTE proteins (AGOs) associate with microRNAs (miRNAs), short interfering RNAs (siRNAs), and other classes of small RNAs to regulate target RNA or target loci. Viral infection in plants induces a potent and highly specific antiviral RNA silencing response characterized by the formation of virus-derived siRNAs. Arabidopsis thaliana has ten AGO genes of which AGO1, AGO2, and AGO7 have been shown to play roles in antiviral defense. A genetic analysis was used to identify and characterize the roles of AGO proteins in antiviral defense against Turnip mosaic virus (TuMV) in Arabidopsis. AGO1, AGO2 and AGO10 promoted anti-TuMV defense in a modular way in various organs, with AGO2 providing a prominent antiviral role in leaves. AGO5, AGO7 and AGO10 had minor effects in leaves. AGO1 and AGO10 had overlapping antiviral functions in inflorescence tissues after systemic movement of the virus, although the roles of AGO1 and AGO10 accounted for only a minor amount of the overall antiviral activity. By combining AGO protein immunoprecipitation with high-throughput sequencing of associated small RNAs, AGO2, AGO10, and to a lesser extent AGO1 were shown to associate with siRNAs derived from silencing suppressor (HC-Pro)-deficient TuMV-AS9, but not with siRNAs derived from wild-type TuMV. Co-immunoprecipitation and small RNA sequencing revealed that viral siRNAs broadly associated with wild-type HC-Pro during TuMV infection. These results support the hypothesis that suppression of antiviral silencing during TuMV infection, at least in part, occurs through sequestration of virus-derived siRNAs away from antiviral AGO proteins by HC-Pro. These findings indicate that distinct AGO proteins function as antiviral modules, and provide a molecular explanation for the silencing suppressor activity of HC-Pro.

Mexico is a center of origin for several economically important plants including maize, cotton, and cocoa. Maize represents more than a food crop, has been declared a biological, cultural, agricultural and economic patrimony, and is linked to the national identity of Mexicans. In this review, we describe the historic and current use of genetically modified plants in Mexico and factors that contributed to the development of the biosafety regulation. We developed a database containing all permit applications received by the government to release genetically modified plants. A temporal and geographical analysis identified the plant species that have been authorized for experimental purposes, pilot programs, or commercial production, the geographic areas where they have been released, and the traits that have been introduced. Results show that Mexico has faced a dual challenge: accepting the benefits of genetically modified plants and their products, while protecting native plant biodiversity.

Viral diseases of plants cause important economic losses due to reduction in crop quality and quantity to the point of threatening food security in some countries. Given the reduced availability of natural sources, genetic resistance to viruses has been successfully engineered for some plant-virus combinations. A sound understanding of the basic mechanisms governing plant-virus interactions, including antiviral RNA silencing, is the foundation to design better management strategies and biotechnological approaches to engineer and implement antiviral resistance in plants. In this review, we present current molecular models to explain antiviral RNA silencing and its application in basic plant research, biotechnology and genetic engineering.

Kherbet El Dieb, north of Aleppo, is one of 24 Syrian villages involved in a participatory plant breeding (PPB) initiative started by the International Center for Agricultural Research in Dry Areas (ICARDA). Yields there have increased since the farmers have begun using varieties developed through the PPB program. PPB is one of the most common types of benefi t sharing related to farmers' rights as the concept is outlined in the International Treaty on Plant Genetic Resources for Food and Agriculture. Combining farmers' knowledge with that of professional breeders, this approach enables the farmers to benefi t from their contribution to the global genetic pool by adding value to their crops, improving their livelihoods and increasing their incomes. However, as the name indicates, the main principle of PPB is participation, and this is a signature characteristic of the barley breeding initiative in Syria.Fawaz Al-Abboud Al-Hassoun, a farmer in Kherbet El Dieb who took part in the project, is very happy with the participatory approach and the resulting varieties. The productivity of the new varieties is high because of their increased resistance to drought and cold and, thus, they have been adopted by many of the farmers in the village.This case study describes how PPB evolved in Syria and how benefi ts have been generated through local action research in which farmers and breeders are engaged in a collaborative learning process. The PPB work in Syria also served as a learning ground for PPB in other countries in the region (e