Publications

3995

Abstract‘Candidatus Phytoplasma mali’, is a bacterial pathogen associated with the so-called apple proliferation disease in Malus × domestica. The pathogen manipulates its host with a set of effector proteins, among them SAP11CaPm, which shares similarity to SAP11AYWB from ‘Candidatus Phytoplasma asteris’. SAP11AYWB interacts and destabilizes the class II CIN transcription factors of Arabidopsis thaliana, namely AtTCP4 and AtTCP13 as well as the class II CYC/TB1 transcription factor AtTCP18, also known as BRANCHED1 being an important factor for shoot branching. It has been shown that SAP11CaPm interacts with the Malus × domestica orthologues of AtTCP4 (MdTCP25) and AtTCP13 (MdTCP24), but an interaction with MdTCP16, the orthologue of AtTCP18, has never been proven. The aim of this study was to investigate this potential interaction and close a knowledge gap regarding the function of SAP11CaPm. A Yeast two-hybrid test and Bimolecular Fluorescence Complementation in planta revealed that SAP11CaPm interacts with MdTCP16. MdTCP16 is known to play a role in the control of the seasonal growth of perennial plants and an increase of MdTCP16 gene expression has been detected in apple leaves in autumn. In addition to this, MdTCP16 is highly expressed during phytoplasma infection. Binding of MdTCP16 by SAP11CaPm might lead to the induction of shoot proliferation and early bud break, both of which are characteristic symptoms of apple proliferation disease.

Bois noir, an economically important disease of grapevine yellows that causes significant economic losses in wine production, is associated with ‘Candidatus Phytoplasma solani’ and transmitted to grapevines by cixiids Hyalesthes obsoletus and Reptalus panzeri. Polyphagous planthopper Dictyophara europaea, commonly found in natural habitats, harbors phytoplasmas from distinct groups and is an alternative vector in the open epidemiological cycles of the Flavescence dorée phytoplasma in grapevine in European vineyards. This study addresses the role of D. europaea in the transmission cycle(s) of ‘Ca. P. solani’ among wild habitats, natural reservoir plants, and the vineyard agroecosystem using MLSA and transmission trials with naturally infected adults to grapevine and Catharanthus roseus. The infection rates of D. europaea ranged from 7% to 13% in diverse locations, while reservoir herbaceous plants were infected in the amount of 29%. A total of 13 CaPsol MLSA genotypes were detected in D. europaea (7) and plants (8). Nine of them corresponded to previously identified genotypes. Two new genotypes were found in D. europaea (tuf-b1/S1/V14/Rqg50-sv1 and tuf-b1/S18/V14/Rqg50-sv1) and one in Convolvulus arvensis (tuf-b1/S1/V2-TA/Rqg31-sv1), whereas one was shared by two hosts, Crepis foetida and Daucus carota (tuf-b1/S1/V2-TA/STOL-sv1). Naturally infected D. europaea successfully transmitted the tuf-b1/S1/V2-TA/STOL type to five grapevines and six periwinkles, tuf-b1/S1/V2-TA/Rqg31 to one grapevine, and tuf-b1/S1/V2-TA/Rqg50 to one periwinkle, indicating that D. europaea is an intermediate vector in CaPsol epidemiological cycles.

It was shown that the SAP11 effector of different Candidatus Phytoplasma can destabilize some TEOSINE BRANCHES/CYCLOIDEA/PROLIFERATING CELL FACTORs (TCPs), resulting in plant phenotypes such as witches’ broom and crinkled leaves. Some SAP11 exclusively localize in the nucleus, while the others localize in the cytoplasm and the nucleus. The SAP11-like effector of Candidatus Phytoplasma mali strain PM19 (SAP11PM19) localizes in both compartments of plant cells. We show here that SAP11PM19 can destabilize TCPs in both the nucleus and the cytoplasm. However, expression of SAP11PM19 exclusively in the nucleus resulted in the disappearance of leaf phenotypes while still showing the witches’ broom phenotype. Moreover, we show that SAP11PM19 can not only destabilize TCPs but also relocalizes these proteins in the nucleus. Interestingly, three different transgenic Nicotiana species expressing SAP11PM19 show all the same witches’ broom phenotype but different leaf phenotypes. A possible mechanism of SAP11-TCP interaction is discussed.

El cultivo de papa representa en nuestro país una fuente de divisas y genera gran cantidad de empleos. Hasta la fecha no existe un estudio formal sobre la fluctuación poblacional de Bactericera cockerelli y Candidatus liberibacter. Este estudio se realizó con el propósito de determinar la dinámica poblacional de Bactericera cockerelli y la incidencia de Candidatus liberibacter en papa, el cual se llevó a cabo en los municipios Jinotega, La Concordia, San Rafael del Norte y Yalí, del departamento de Jinotega, en el periodo comprendido de febrero a septiembre del 2014.  El levantamiento de datos se desarrolló en 4 fincas de papa. En cada finca se ubicaron 30 trampas amarillas pegajosas y 30 estaciones para el muestreo visual. Los insectos Bactericera cockerelli encontrados, así como los síntomas de la enfermedad detectados en campo, se identificaron con ayuda de la guía temática utilizada por los especialistas fitosanitarios del Instituto de Protección y Sanidad Agropecuaria (IPSA). Se evaluó el número de insectos capturados en las trampas amarillas y el númede insectos observados, el número de plantas con síntomas de Candidatus liberibacter y la incidencia de daño en tubérculos en las fincas de papa. De acuerdo a los resultados obtenidos se demostró que las poblaciones de Bactericera cockerelli se presentaron en papa, desde marzo 14 hasta mayo 23, con el máximo pico poblacional abril 25, en el ciclo de primera y de junio 23 hasta septiembre 02, con el máximo pico poblacional en julio 22, en el ciclo de postrera; la incidencia de Candidatus liberibacter en papa fue mayor en el ciclo de primera que en postrera y la incidencia de Candidatus liberibacter en tubérculos fue mayor en la finca Buenos Aires con 72%, El Aguacate 1 presentó 32%, Las Piedras 23% y El Aguacate 2, 16%.

AbstractNatural microbial communities are phylogenetically and metabolically diverse. In addition to underexplored organismal groups1, this diversity encompasses a rich discovery potential for ecologically and biotechnologically relevant enzymes and biochemical compounds2,3. However, studying this diversity to identify genomic pathways for the synthesis of such compounds4 and assigning them to their respective hosts remains challenging. The biosynthetic potential of microorganisms in the open ocean remains largely uncharted owing to limitations in the analysis of genome-resolved data at the global scale. Here we investigated the diversity and novelty of biosynthetic gene clusters in the ocean by integrating around 10,000 microbial genomes from cultivated and single cells with more than 25,000 newly reconstructed draft genomes from more than 1,000 seawater samples. These efforts revealed approximately 40,000 putative mostly new biosynthetic gene clusters, several of which were found in previously unsuspected phylogenetic groups. Among these groups, we identified a lineage rich in biosynthetic gene clusters (‘Candidatus Eudoremicrobiaceae’) that belongs to an uncultivated bacterial phylum and includes some of the most biosynthetically diverse microorganisms in this environment. From these, we characterized the phospeptin and pythonamide pathways, revealing cases of unusual bioactive compound structure and enzymology, respectively. Together, this research demonstrates how microbiomics-driven strategies can enable the investigation of previously undescribed enzymes and natural products in underexplored microbial groups and environments.

‘Candidatus Phytoplasma pruni’ infection in cherries causes small, misshapen fruit with poor color and taste, rendering the fruit unmarketable. However, this is a disease with a long development cycle and a scattered, nonuniform symptom distribution in the early stages. To better understand the biology as well as the relationship between pathogen titer and disease expression, we carried out seasonal, spatial, and temporal examinations of ‘Ca. P. pruni’ titer and distribution in infected orchard-grown trees. Sequential sampling of heavily infected trees revealed marked seasonal patterns, with differential accumulation in woody stem and leaf tissues and, most notably, within fruit in the early stages of development from bloom to pit hardening. Furthermore, mapping phytoplasma distribution and titer in trees at different stages of infection indicated that infection proceeds through a series of stages. Initially, infection spreads basipetally and accumulates in the roots before populating aerial parts of the trees from the trunk upward, with infection of specific tissues and limbs followed by an increasing phytoplasma titer. Finally, we observed a correlation between phytoplasma titer and symptom severity, with severe symptom onset associated with three to four orders of magnitude more phytoplasma than mild symptoms. Cumulatively, these data aid in accurate sampling and management decision-making and furthers our understanding of disease development.