Presence of 16SrIV phytoplasmas of subgroups A, D and E in planthopper Haplaxius crudus Van Duzee insects in Yucatán, Mexico.

The present study was carried out to determine if group 16SrIV phytoplasmas, causing lethal yellowing (LY) disease, are present in Haplaxius crudus Van Duzee (Hemiptera: Cixiidae) insects associated with palms in Yucatán, Mexico. Haplaxius crudus feral insects were captured from palm foliage at two locations (Chicxulub Puerto and CICY, Mérida, where LY-type diseases are active) and evaluated individually for the presence of phytoplasma DNA by a group 16SrIV-specific nested PCR assay. The results showed positive detection in H. crudus insects in a proportion of 2.7% (of the total 2726 analyzed) during a 3-year period of study. The percentage of detection was different for each site, 5.9% positive of 799 insects from Mérida and 1.7% of 1927 from Chicxulub Puerto. Positive detections were also obtained in extracts from 5.3 to 1.2% of males and females, respectively. Sequencing and in silico RFLP and phylogenetic analyses of PCR-amplified rDNA products indicated that H. crudus insects from Chicxulub Puerto harbored phytoplasma strains of subgroups 16SrIV-A or 16SrIV-D, whereas in insects from Mérida the strains found were 16SrIV-A, 16SrIV-D or 16SrIV-E. The diversity of subgroup strains detected in H. crudus coincided with strains previously identified in palms showing LY-type disease syndromes in Yucatán thereby implicating H. crudus as a candidate vector of 16SrIV phytoplasmas in this region of Mexico.

Partial Gene Sequencing of CYP1A, Vitellogenin, and Metallothionein in Mosquitofish Gambusia yucatana and Gambusia sexradiata.

Ground characteristics in the Yucatan Peninsula make recovery and treatment of wastewater very expensive. This situation has contributed to an increase of pollutants in the aquifer. Unfortunately, studies related to the effects of those pollutants in native organisms are scarce. The aim of this work was to obtain partial sequences of widely known genes used as biomarkers of pollutant effect in Gambusia yucatana and Gambusia sexradiata. The studied genes were: cytochrome P450 1A (CYP1A); vitellogenin (VTG); metallothionein (MT), and two housekeeping genes, 18S and ß-actin. From reported sequences of Gambusia affinis, primers were designed and amplification was done in the local Gambusia species exposed for 48 h to gasoline (100 µL/L, stirred for 24 h pre-exposure). Preliminary results revealed partial sequences of all genes with an approximate average length of 200 bp. BLAST analysis of found sequences indicated a minimum of 97% identity with reported sequences for G. affinis or Gambusia holbrooki showing great similarity.

Genome-wide in silico identification of GPI proteins in Mycosphaerella fijiensis and transcriptional analysis of two GPI-anchored ß-1,3-glucanosyltransferases.

The hemibiotrophic fungus Mycosphaerella fijiensis is the causal agent of black Sigatoka (BS), the most devastating foliar disease in banana (Musa spp.) worldwide. Little is known about genes that are important during M. fijiensis-Musa sp. interaction. The fungal cell wall is an attractive area of study because it is essential for maintenance of cellular homeostasis and it is the most external structure in the fungal cell and therefore mediates the interaction of the pathogen with the host. In this manuscript we describe the in silico identification of glycosyl phosphatidylinositol-protein (GPI) family in M. fijiensis, and the analysis of two ß-1,3-glucanosyltrans-ferases (Gas), selected by homology with fungal pathogenicity factors. Potential roles in pathogenesis were evaluated through analyzing expression during different stages of black Sigatoka disease, comparing expression data with BS symptoms and fungal biomass inside leaves. Real-time quantitative RT-PCR showed nearly constant expression of MfGAS1 with slightly increases (about threefold) in conidia and at speck-necrotrophic stage during banana-pathogen interaction. Conversely, MfGAS2 expression was increased during biotrophy (about seven times) and reached a maximum at speck (about 23 times) followed by a progressive decrease in next stages, suggesting an active role in M. fijiensis pathogenesis.

Occurrence of a 16SrIV Group Phytoplasma not Previously Associated with Palm Species in Yucatan, Mexico.

The occurrence of 16SrIV group phytoplasmas in palm species Sabal mexicana and Pseudophoenix sargentii is reported here for the first time. Palm trees showed leaf decay and leaf yellowing syndromes, respectively. An amplification product (1.4 kb) was obtained in symptomatic S. mexicana (18 of 21) and symptomatic P. sargentii (1 of 1) palm trees sampled in different locations in Yucatan State, Mexico; five of the positive S. mexicana and the positive P. sargentii trees died. The identity of the phytoplasmas from these species was determined by restriction fragment length polymorphism profiling with restriction enzymes AluI and HinfI, showing there could be two phytoplasma strains of the 16SrIV group. In one S. mexicana palm, the profile was the same as observed with these enzymes for phytoplasmas of 16SrIV-A subgroup, previously associated with Cocos nucifera palm trees and, in the rest of the trees, including the P. sargentii palm, the profile was for phytoplasmas of the 16SrIV-D subgroup. These identities were supported by analyses of the amplicons obtained by nested polymerase chain reaction by nucleotide-nucleotide BLAST analysis. Geographical distribution of the association S. mexicana/16SrIV group phytoplasmas was found widely dispersed in Yucatan State. A potential role of S. mexicana palm trees as a permanent source of phytoplasma inoculum is suggested. In addition to P. sargentii, other palm species (Thrinax radiata and C. nucifera) coexisting with S. mexicana trees were also sampled and analyzed.