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We are delighted to preface this book, which is the result of our institutions' shared commitment to advancing knowledge and promoting action to preserve biodiversity. The Nagoya Protocol has revolutionised research on the living world by formally incorporating the issues of access and appropriation, justice and equity, into its everyday activities. As institutions and scientists working with biological resources and the associated knowledge, it compels us to examine the key ethical and econo...

A landmark text in global biodiversity governance, the Nagoya Protocol was intended to put an end to the uncompensated exploitation of natural resources and knowledge originating in the Global South. Its stated objectives were to establish greater justice and equity between providers and users of genetic resources, to foreground the contributions and knowledge of indigenous peoples and local communities, and to decolonise research, all while promoting the conservation of biodiversity. Thirty years on from the Convention on Biological Diversity from which it originated, the authors examine the legal and practical outcomes of this virtuous framework, which came into force in 2014. Although it has certainly fostered greater recognition of the plurality of knowledge and advanced the traceability of resources, the Protocol has also helped to impose a narrowly market-oriented understanding of nature and knowledge, exacerbating demands for recognition and ownership in the Global South, and effectively restricting access to biodiversity in an era of globalised research. This book presents an interdisciplinary dialogue informed by the experiences of researchers and conservation stakeholders (local communities, managers of collections and natural parks). Looking beyond the Nagoya Protocol, it invites us to question the relationships between societies and nature in light of the ecological emergency. It is intended for anyone with an interest in the economics of biodiversity and environmental justice.

International audience; Xanthomonas oryzae pv. oryzae (Xoo) strains that cause bacterial leaf blight (BLB) limit rice (Oryza sativa) production and require breeding more resistant varieties. Transcription activator-like effectors (TALEs) activate transcription to promote leaf colonization by binding to specific plant host DNA sequences termed effector binding elements (EBEs). Xoo major TALEs universally target susceptibility genes of the SWEET transporter family. TALE-unresponsive alleles of clade III OsSWEET susceptibility gene promoter created with genome editing confer broad resistance on Asian Xoo strains. African Xoo strains rely primarily on the major TALE TalC, which targets OsSWEET14. Although the virulence of a talC mutant strain is severely impaired, abrogating OsSWEET14 induction with genome editing does not confer equivalent resistance on African Xoo. To address this contradiction, we postulated the existence of a TalC target susceptibility gene redundant with OsSWEET14. Bioinformatics analysis identified a rice locus named ATAC composed of the INCREASED LEAF INCLINATION 2 (ILI2) gene and a putative lncRNA that are shown to be bidirectionally upregulated in a TalC-dependent fashion. Gain-of-function approaches with designer TALEs inducing ATAC sequences did not complement the virulence of a Xoo strain defective for SWEET gene activation. While editing the TalC EBE at the ATAC loci compromised TalC-mediated induction, multiplex edited lines with mutations at the OsSWEET14 and ATAC loci remained essentially susceptible to African Xoo strains. Overall, this work indicates that ATAC is a probable TalC off-target locus but nonetheless documents the first example of divergent transcription activation by a native TALE during infection.

International audience; Xanthomonas phaseoli pv. manihotis (Xpm) and X. cassavae (Xc) are two bacterial pathogens attacking cassava. Cassava bacterial blight (CBB) is a systemic disease caused by Xpm, which might have dramatic effects on plant growth and crop production. Cassava bacterial necrosis is a nonvascular disease caused by Xc with foliar symptoms similar to CBB, but its impacts on the plant vigour and the crop are limited. In this review, we describe the epidemiology and ecology of the two pathogens, the impacts and management of the diseases, and the main research achievements for each pathosystem. Because Xc data are sparse, our main focus is on Xpm and CBB.

Designed to reach the widest possible audience, this volume showcases some of the research projects which best illustrate the commitment of the French National Research Institute for Sustainable Development (IRD) to biodiversity and sustainable development. Among today's many pressing environmental challenges, protecting biodiversity is probably one of the most complex, since it cannot be understood independently of its interactions with the human societies who live with it, use it, manage it, destroy and, occasionally, protect it. As the examples contained herein demonstrate, biodiversity can no longer be confined by narrow academic boundaries. On the contrary, it is a subject inextricably linked with all of the major dynamics, human and non-human, which shape the global and local changes we currently face. In this respect, the present volume is testament to the commitment demonstrated by IRD and its partners to a vision of scientific endeavour which yields tangible, utilisable knowledge for the Global South, sustainability science in the strongest sense of the term, allowing our planet and its biodiversity to thrive in the long term.

Effective and durable disease resistance for bacterial blight (BB) of rice is a continuous challenge due to the evolution and adaptation of the pathogen,Xanthomonas oryzaepv.oryzae(Xoo), on cultivated rice varieties. Fundamental to this pathogens' virulence is transcription activator-like (TAL) effectors that activate transcription of host genes and contribute differently to pathogen virulence, fitness or both. Host plant resistance is predicted to be more durable if directed at strategic virulence factors that impact both pathogen virulence and fitness. We characterized Tal7b, a minor-effect virulence factor that contributes incrementally to pathogen virulence in rice, is a fitness factor to the pathogen and is widely present in geographically diverse strains ofXoo. To identify sources of resistance to this conserved effector, we used a highly virulent strain carrying a plasmid borne copy of Tal7b to screen an indica multi-parent advanced generation inter-cross (MAGIC) population. Of 18 QTL revealed by genome-wide association studies and interval mapping analysis, six were specific to Tal7b (qBB-tal7b). Overall, 150 predicted Tal7b gene targets overlapped with qBB-tal7bQTL. Of these, 21 showed polymorphisms in the predicted effector binding element (EBE) site and 23 lost the EBE sequence altogether. Inoculation and bioinformatics studies suggest that the Tal7b target in one of the Tal7b-specific QTL, qBB-tal7b-8, is a disease susceptibility gene and that the resistance mechanism for this locus may be through loss of susceptibility. Our work demonstrates that minor-effect virulence factors significantly contribute to disease and provide a potential new approach to identify effective disease resistance.

International audience; Rice bacterial leaf blight (BLB) is caused by Xanthomonas oryzae pv. oryzae (Xoo) which injects Transcription Activator-Like Effectors (TALEs) into the host cell to modulate the expression of target disease susceptibility genes. Xoo major-virulence TALEs universally target susceptibility genes of the SWEET sugar transporter family. TALE-unresponsive alleles of OsSWEET genes have been identified in the rice germplasm or created by genome editing and confer resistance to BLB. In recent years, BLB has become one of the major biotic constraints to rice cultivation in Mali. To inform the deployment of alternative sources of resistance in this country, rice lines carrying alleles of OsSWEET14 unresponsive to either TalF (formerly Tal5) or TalC, two important TALEs previously identified in West African Xoo, were challenged with a panel of strains recently isolated in Mali and were found to remain susceptible to these isolates. The characterization of TALE repertoires revealed that talF and talC specific molecular markers were simultaneously present in all surveyed Malian strains, suggesting that the corresponding TALEs are broadly deployed by Malian Xoo to redundantly target the OsSWEET14 gene promoter. Consistent with this, the capacity of most Malian Xoo to induce OsSWEET14 was unaffected by either talC- or talF-unresponsive alleles of this gene. Long-read sequencing and assembly of eight Malian Xoo genomes confirmed the widespread occurrence of active TalF and TalC variants and provided a detailed insight into the diversity of TALE repertoires. All sequenced strains shared nine evolutionary related tal effector genes. Notably, a new TalF variant that is unable to induce OsSWEET14 was identified. Furthermore, two distinct TalB variants were shown to have lost the ability to simultaneously induce two susceptibility genes as previously reported for the founding members of this group from strains MAI1 and BAI3. Yet, both new TalB variants retained the ability to induce one or the other of the two susceptibility genes. These results reveal molecular and functional differences in tal repertoires and will be important for the sustainable deployment of broad-spectrum and durable resistance to BLB in West Africa.

Main conclusion The overexpression of RXam1 leads to a reduction in bacterial growth of XamCIO136, suggesting that RXam1 might be implicated in strain-specific resistance. Cassava bacterial blight (CBB) caused by Xanthomonas axonopodis pv. manihotis (Xam) is a prevalent disease in all regions, where cassava is cultivated. CBB is a foliar and vascular disease usually controlled through host resistance. Previous studies have found QTLs explaining resistance to several Xam strains. Interestingly, one QTL called XM5 that explained 13% of resistance to XamCIO136 was associated with a similar fragment of the rice Xa21-resistance gene called PCR250. In this study, we aimed to further identify and characterize this fragment and its role in resistance to CBB. Screening and hybridization of a BAC library using the molecular marker PCR250 as a probe led to the identification of a receptor-like kinase similar to Xa21 and were called RXam1 (R esistance to Xam 1). Here, we report the functional characterization of susceptible cassava plants overexpressing RXam1. Our results indicated that the overexpression of RXam1 leads to a reduction in bacterial growth of XamCIO136. This suggests that RXAM1 might be implicated in strain-specific resistance to XamCIO136.

Most Xanthomonas species translocate Transcription Activator-Like (TAL) effectors into plant cells where they function like plant transcription factors via a programmable DNA-binding domain. Characterized strains of rice pathogenic X. oryzae pv. oryzae harbor 9-16 different tal effector genes, but the function of only a few of them has been decoded. Using sequencing of entire genomes, we first performed comparative analyses of the complete repertoires of TAL effectors, herein referred to as TALomes, in three Xoo strains forming an African genetic lineage different from Asian Xoo. A phylogenetic analysis of the three TALomes combined with in silico predictions of TAL effector targets showed that African Xoo TALomes are highly conserved, genetically distant from Asian ones, and closely related to TAL effectors from the bacterial leaf streak pathogen Xanthomonas oryzae pv. oryzicola (Xoc). Nine clusters of TAL effectors could be identified among the three TALomes, including three showing higher levels of variation in their repeat variable diresidues (RVDs). Detailed analyses of these groups revealed recombination events as a possible source of variation among TAL effector genes. Next, to address contribution to virulence, nine TAL effector genes from the Malian Xoo strain MAI1 and four allelic variants from the Burkinabe Xoo strain BAI3, thus representing most of the TAL effector diversity in African Xoo strains, were expressed in the TAL effector-deficient X. oryzae strain X11-5A for gain-of-function assays. Inoculation of the susceptible rice variety Azucena lead to the discovery of three TAL effectors promoting virulence, including two TAL effectors previously reported to target the susceptibility (S) gene OsSWEET14 and a novel major virulence contributor, TalB. RNA profiling experiments in rice and in silico prediction of EBEs were carried out to identify candidate targets of TalB, revealing OsTFX1, a bZIP transcription factor previously identified as a bacterial blight S gene, and OsERF#123, which encodes a subgroup IXc AP2/ERF transcription factor. Use of designer TAL effectors demonstrated that induction of either gene resulted in greater susceptibility to strain X11-5A. The induction of OsERF#123 by BAI3 Delta 1, a talB knockout derivative of BAI3, carrying these designer TAL effectors increased virulence of BAI3 Delta 1, validating OsERF#123 as a new, bacterial blight S gene.

Prevalence of Xanthomonas translucens, which causes cereal leaf streak (CLS) in cereal crops and bacterial wilt in forage and turfgrass species, has increased in many regions in recent years. Because the pathogen is seedbome in economically important cereals, it is a concern for international and interstate germplasm exchange and, thus, reliable and robust protocols for its detection in seed are needed. However, historical confusion surrounding the taxonomy within the species has complicated the development of accurate and reliable diagnostic tools for X. translucens. Therefore, we sequenced genomes of 15 X. translucens strains representing six different pathovars and compared them with additional publicly available X. translucens genome sequences to obtain a genome-based phylogeny for robust classification of this species. Our results reveal three main clusters: one consisting of pv. cerealis, one consisting of pvs. undulosa and translucens, and a third consisting of pvs. arrhenatheri, granzinis, phlei, and poae. Based on genomic differences, diagnostic loop-mediated isothermal amplification (LAMP) primers were developed that clearly distinguish strains that cause disease on cereals, such as pvs. undulosa, translucens, hordei, and secalis, from strains that cause disease on non cereal hosts, such as pvs. arrhenatheri, cerealis, graminis, phlei, and poae. Additional LAMP assays were developed that selectively amplify strains belonging to pvs. cerealis and poae, distinguishing them from other pathovars. These primers will be instrumental in diagnostics when implementing quarantine regulations to limit further geographic spread of X. translucens pathovars.

Understanding the diversity of pathogen populations in a regional scale is crucial in order to develop strategies for sustainable control of plant diseases. Our work deals with the study of the plant pathogenic bacterium Xanthomonas axonopodis pv. manihotis (Xam), which is the causal agent of cassava bacterial blight (CBB). CBB occurs in the tropics including in West-Africa where it has recently been reported in Burkina Faso and Ivory Coast, sometimes imposing severe yield losses to cassava producers. The status of CBB in Mali still remains unstudied. To fill this gap, preliminary surveys were conducted in Dec. 2015 in two cassava production regions. Nearly 80 leaf samples were processed, leading to the isolation of about 50 Xam candidate isolates. Of these, 40 strains of Xanthomonas axonopodis pv. manihotis were validated through molecular diagnostic tests and pathogenicity assays. This study represents the first demonstration for the presence of CBB in Mali and enabled to initiate the establishment of a first collection of national Xam strains. Secondly, a MLVA strategy (Multiple-Locus Variable number tandem repeat Analysis) was developed based on the analysis of 14 microsatellites (VNTR) in order to assess the genetic diversity of the 40 strains isolated from our two regions under study, Bamako and Segou, which are 250km distant. Our results demonstrate a greater diversity in populations of the Bamako region relative to that of Segou, with reference to the values of diversity indices. Also, comparison of all strains of Mali with a collection of 215 strains from border regions in Burkina Faso suggested that the Malian strains are less diversified. Further surveys covering most areas of cassava production in Mali are in progress to better understand Xam invasion routes in this country.

Plant disease is a major challenge to agriculture worldwide, and it is exacerbated by abiotic environmental factors. During some plant-pathogen interactions, heat stress allows pathogens to overcome host resistance, a phenomenon which could severely impact crop productivity considering the global warming trends associated with climate change. Despite the importance of this phenomenon, little is known about the underlying molecular mechanisms. To better understand host plant responses during simultaneous heat and pathogen stress, we conducted a transcriptomics experiment for rice plants (cultivar IRBB61) containing Xa7, a bacterial blight disease resistance (R) gene, that were infected with Xanthomonas oryzae, the bacterial blight pathogen of rice, during high temperature stress. Xa7-mediated resistance is unusual relative to resistance mediated by other Rgenes in that it functions better at high temperatures. Using RNA-Seq technology, we identified 8,499 differentially expressed genes as temperature responsive in rice cultivar IRBB61 experiencing susceptible and resistant interactions across three time points. Notably, genes in the plant hormone abscisic acid biosynthesis and response pathways were up-regulated by high temperature in both mock-treated plants and plants experiencing a susceptible interaction and were suppressed by high temperature in plants exhibiting Xa7-mediated resistance. Genes responsive to salicylic acid, an important plant hormone for disease resistance, were down-regulated by high temperature during both the susceptible and resistant interactions, suggesting that enhanced Xa7-mediated resistance at high temperature is not dependent on salicylic acid signaling. A DNA sequence motif similar to known abscisic acid-responsive cis-regulatory elements was identified in the promoter region upstream of genes up-regulated in susceptible but down-regulated in resistant interactions. The results of our study suggest that the plant hormone abscisic acid is an important node for cross-talk between plant transcriptional response pathways to high temperature stress and pathogen attack. Genes in this pathway represent an important focus for future study to determine how plants evolved to deal with simultaneous abiotic and biotic stresses.

Phytopathogens have developed elaborate mechanisms to attenuate the defense response of their host plants, including convergent evolution of complex pathways for production of the GA phytohormones, which were actually first isolated from the rice fungal pathogen Gibberella fujikuroi. The rice bacterial pathogen Xanthomonas oryzae pv. oryzicola (Xoc) has been demonstrated to contain a biosynthetic operon with cyclases capable of producing the universal GA precursor ent-kaurene. Genetic (knock-out) studies indicate that the derived diterpenoid serves as a virulence factor for this rice leaf streak pathogen, serving to reduce the jasmonic acid-mediated defense response. Here the functions of the remaining genes in the Xoc operon are elucidated and the distribution of the operon in X. oryzae is investigated in over 100 isolates. The Xoc operon leads to production of the bioactive GA(4), an additional step beyond production of the penultimate precursor GA(9) mediated by the homologous operons recently characterized from rhizobia. Moreover, this GA biosynthetic operon was found to be widespread in Xoc (> 90%), but absent in the other major X. oryzae pathovar. These results indicate selective pressure for production of GA(4) in the distinct lifestyle of Xoc, and the importance of GA to both fungal and bacterial pathogens of rice.

Studies on pathogenic agents of cultivated plants are generally organised on a binomial basis with examination of a host plant and specific parasites or pests. As cassava in Africa has few important pests and they display a limited range of biological features and relations with the host, it was feasible for ORSTOM (L'Institutfrançaise de recherche scientifique pour le developpement en coopératon) researchers to study each of them over a period of 25 years in Côte d'lvoire, Congo and Togo and such work is currently in progress in Benin and France. The diseases and pests concerned are African cassava mosaic disease and its whitefly vector (Bemisia tahaci), cassava bacterial blight caused by Xanthomonas campestris pv manihotis, cassava mealybug (Phenacoccus manihoti), and cassava green mite (Mononychelus progresivus). Research initially concerned only specific cassava-pathogen or cassava-pest combinations, without attention being paid to the system as a whole, despite obvious epidemic convergences resulting from a common environment, analogies between effects on the host plant and probable interactions between the various pests of the same crop. A biocenotic approach was developed to integrate the various research activities. It is aimed at analysis of the functioning of plant-pathogen and plant-pest systems and enables the design and evaluation of options for integrated management. 'Transversal' comparisons of cassava parasite models cover pathogenic agents (pests and diseases) and their variability, their biological cycles and the climatic factors affecting them, relations with the host (genetic variability, physiology and crop management), the effect of entomophagous species and entomopathogens on phytophagous pests and the integration potential of modelling. The ORSTOM studies show the complexity of the ecology of pathogenic agents and pests in the cassava biocenosis. The extent of the cassava cropping area and the variety of production situations, the variability of pests (phytophagous and entomophagous organisms) and diseases and the many interactions between the factors regulating epidemic mechanisms leads to a complex mosaic whose structure is described. The various sequences of analysis of a system of parasite constraints are shown in matrix form (variability of pathogenic agents, vectors and phytophagous organisms, host-parasite relation modes, epidemiology and population dynamics, modelling) for the various organisms investigated to date. The analysis reveals the fundamental achievements and gaps in knowledge and also the most appropriate areas for combining approaches. The body of knowledge assembled at different sites, during different periods and concerning a variety of organisms and the analysis of this knowledge show that it is not necessary at this stage to collect new information but to make a synthesis (modelling) that will open up original lines of research with combinations of approaches and solutions.Key Words: Cassava, pests and diseases, epidemiology and population dynamics, life cycles, host-parasite relations, natural enemies, vectors, modelling, integrated pest management, Africa Les travaux sur les agents pathogènes des plantes cultivées s'organisent le plus souvent selon une approche binomiale qui prend en compte une plante et un parasite ou une plante et un ravageur. Dans le cas du manioc en Afrique, pour des ennemis peu nombreux et qui offrent une palette très diverse de traits biologiques et de relations avec la plante, les recherches ont été conduites depuis près d'un quart de siècle par les chercheurs de l'ORSTOM (L'Institut française de recherche scientitique pour le developpement en coopératon) en Côte d'lvoire, au Congo et au Togo et sont actuellement poursuivies au Bénin et en France. Il s'agit de la mosaïque africaine du manioc et de son insecte vecteur Bemisia tabaci, de la bactériose vasculaire dont l'agent est Xanthomonas campestris pv manihotis, de la cochenille du manioc Phenacoccus manihoti, et de l'acarien vert, Mononychellus progresivus. Les travaux se sont d'abord attachés aux seuls couples manioc-maladie ou manioc-ravageur, sans considérer le système parasitaire dans son ensemble en dépit de convergences évidentes dues à un environnement common, à des analogies d 'effet sur la plante hôte et à des interactions probables entre les différents ennemis de la même culture. Nous avons ici élaboré une approche biocénotique qui permet d'intégrer différentes actions de recherche, orientée vers l'analyse du fonctionnement des systèmes plante-parasites et plante-ravageurs et qui permet de formuler et d'évaluer les options de gestion intégrée de cette biocénose parasitaire. La comparaison "transversale" des modèles parasitaires du manioc aborde successivement les agents pathogènes (maladies et ravageurs) et leurs variabilités, leurs cycles biologiques et les facteurs environnementaux qui les conditionnent, les relations avec la plante (variabilité génétique, physiologie et conduite de la culture), l'incidence des entomophages et entomopathogènes sur les phytophages et les perspectives d 'intégration offertes par la modélisation. Les études menées par l'ORSTOM mettent en évidence la complexité de l'écologie des ravageurs et des agents pathogènes de la biocénose manioc. L'étendue de l'aire de culture du manioc, la diversité des situations de production, la variabilité des parasites (maladies, phytophages etentomophages), la multiplicité des modes de relation entre la plante et ses satellites (parasites, phytophages, entomophages et vecteurs ), le foisonnement des interactions entre les facteurs qui règlent les mécanismes épidémiques, font que la connaissance se présente sous l'aspect d'une mosaïque dont nous faisons apparaître la structure. Nous avons représenté de façon matricielle les différentes séquences d'une analyse d'un système de contraintes parasitaires (variabilité des agents pathogènes, des vecteurs et des phytophages; modalités des relations hôte-parasite; épidémiologie et dynamique des populations; modélisation) en regard des différents organismes jusqu'ici etudiés. L'analyse révèle à la fois les acquis fondamentaux et les lacunes de la connaissance, mais aussi les domaines privilégiés d 'une intégration des démarches. La masse des connaissances, obtenues dans des sites différents, à des périodes différentes et sur des organismes variés, ainsi que l'analyse qui en est faite, montre qu'il n'est pas nécessaire à ce stade de recueillir de nouvelles informations, mais de réaliser une synthèse (modéllsation) qui ouvrira des voies de recherche originales dans le sens de l'intégration des approches et des solutions à apporter.Mots Clés: Manioc, parasites et ravageurs, épidémiologie et dynamique des populations, cycles biologiques, relations hôte-parasite, ennemis naturels, vecteurs, modélisation, gestion intégrée, Afrique

Introduced to Africa in the 1970s, cassava bacterial blight caused by Xanthomonas campestris pv. manihotis (XCM) is present in almost all cropping areas. In the past fifteen years, advances have been made inknowledge of the biology and molecular genetics of XCM, host-parasite relationships and epidemiology of the disease. This paper highlights these recent advances and focuses on the potential of the results obtained to facilitate the design of control strategies suitable for small-scale farmers in Africa.Key Words: Xanthomonas campestris pv. manihotis, epidemiology, variability, host-pathogen interactions, control methodsIntroduite en Afrique depuis les années 1970, la bactériose vasculaire du manioc dont l'agent causal est Xanthomonas campestris pv. manihotis y sévit dans la majorité des zones de culture de cette plante. Les études entreprises depuis une quinzaine d'années, dans divers pays africains, ont conduit à une bonne connaissance de l'étiologie et de l' épidémiologie de cette maladie. Cet article met en lumière les développement recents et souligne le potentiel des resultats obtenus pour la mise en place de stratégies de lutte adaptées aux utilieux paysans africains.Mot Clés: Xanthomonas campestris pv. manihotis, épidémiologie, variabilité, relations hôte-parasite, méthodes de lutte

International audience

The rice pathogens Xanthomonas oryzae pathovar (pv.) oryzae and pv. oryzicola produce numerous transcription activator-like (TAL) effectors that increase bacterial virulence by activating expression of host susceptibility genes. Rice resistance mechanisms against TAL effectors include polymorphisms that prevent effector binding to susceptibility gene promoters, or that allow effector activation of resistance genes. This study identifies, in the heirloom variety Carolina Gold Select, a third mechanism of rice resistance involving TAL effectors. This resistance manifests through strong suppression of disease development in response to diverse TAL effectors from both X. oryzae pathovars. The resistance can be triggered by an effector with only 3.5 central repeats, is independent of the composition of the repeat variable di-residues that determine TAL effector binding specificity, and is independent of the transcriptional activation domain. We determined that the resistance is conferred by a single dominant locus, designated Xo1, that maps to a 1.09 Mbp fragment on chromosome 4. The Xo1 interval also confers complete resistance to the strains in the African clade of X. oryzae pv. oryzicola, representing the first dominant resistance locus against bacterial leaf streak in rice. The strong phenotypic similarity between the TAL effector-triggered resistance conferred by Xo1 and that conferred by the tomato resistance gene Bs4 suggests that monocots and dicots share an ancient or convergently evolved mechanism to recognize analogous TAL effector epitopes.