15 research outputs found
Population Structure of the Bacterial Pathogen Xylella fastidiosa among Street Trees in Washington D.C.
Funding for Open Access provided by the UMD Libraries Open Access Publishing Fund.Bacterial leaf scorch, associated with the bacterial pathogen Xylella fastidiosa, is a widely
established and problematic disease of landscape ornamentals in Washington D.C. A multilocus
sequence typing analysis was performed using 10 housekeeping loci for X. fastidiosa
strains in order to better understand the epidemiology of leaf scorch disease in this municipal
environment. Samples were collected from 7 different tree species located throughout
the District of Columbia, consisting of 101 samples of symptomatic and asymptomatic foliage
from 84 different trees. Five strains of the bacteria were identified. Consistent with
prior data, these strains were host specific, with only one strain associated with members of
the red oak family, one strain associated with American elm, one strain associated with
American sycamore, and two strains associated with mulberry. Strains found for asymptomatic
foliage were the same as strains from the symptomatic foliage on individual trees.
Cross transmission of the strains was not observed at sites with multiple species of infected
trees within an approx. 25 m radius of one another. X. fastidiosa strain specificity observed
for each genus of tree suggests a highly specialized host-pathogen relationship
From L-Dopa to Dihydroxyphenylacetaldehyde: A Toxic Biochemical Pathway Plays a Vital Physiological Function in Insects
One protein in Aedes aegypti, classified into the aromatic amino acid decarboxylase (AAAD) family based on extremely high sequence homology (∼70%) with dopa decarboxylase (Ddc), was biochemically investigated. Our data revealed that this predicted AAAD protein use L-dopa as a substrate, as does Ddc, but it catalyzes the production of 3,4-dihydroxylphenylacetaldehyde (DHPAA) directly from L-dopa and apparently has nothing to do with the production of any aromatic amine. The protein is therefore named DHPAA synthase. This subsequently led to the identification of the same enzyme in Drosophila melanogaster, Anopheles gambiae and Culex quinquefasciatus by an initial prediction of putative DHPAA synthase based on sequence homology and subsequent verification of DHPAA synthase identity through protein expression and activity assays. DHPAA is highly toxic because its aldehyde group readily reacts with the primary amino groups of proteins, leading to protein crosslinking and inactivation. It has previously been demonstrated by several research groups that Drosophila DHPAA synthase was expressed in tissues that produce cuticle materials and apparent defects in regions of colorless, flexible cuticular structures have been observed in its gene mutants. The presence of free amino groups in proteins, the high reactivity of DHPAA with the free amino groups, and the genetically ascertained function of the Drosophila DHPAA synthase in the formation of colorless, flexible cuticle, when taken together, suggest that mosquito and Drosophila DHPAA synthases are involved in the formation of flexible cuticle through their reactive DHPAA-mediated protein crosslinking reactions. Our data illustrate how a seemingly highly toxic pathway can serve for an important physiological function in insects