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Abstract

A protein associated with citrus blight (CB), a disease of unknown cause, was partially characterized. The 12 kDa protein, designated p12, is diagnostic of CB and is present in leaves and xylem fluid from roots and stems of CB-affected trees. The protein, and up to six other CB-specific proteins, are readily detected by SDS-PAGE of xylem fluid from CB-affected trees. The partial N-terminal amino acid sequence of p12 was found to be unique based on database searches. A cDNA library from CB-affected root cambium was screened with a 60 bp fragment, obtained by PCR amplification of cDNA with degenerate primers designed using the amino acid sequence of p12, and two clones were selected. These clones were sequenced revealing a 674 nucleotide cDNA with a 393 nt ORF which included sequence predicted by the N-terminal amino acid sequence of p12. The amino acid sequence based on the p12 ORF was found to be up to 49% similar and 31% identical to expansins. Bacterial expression of the cloned ORF, which encodes an 11.8 kDa protein plus an N-terminal hydrophobic signal peptide, produced an immunoreactive protein of the expected size. By northern blot analysis, it was determined that p12 transcripts are present in root and stem cambium, but not in leaves of CB-affected trees, suggesting transport of the protein to leaves. Southern hybridization analysis of citrus genomic DNA indicated that p12 is a citrus encoded protein.

A tomato xylem sap protein represents a new family of small cysteine‐rich proteins with structural similarity to lipid transfer proteins

“…Using MS/MS sequence tags, we identified the coding sequence for this protein in the TIGR tomato gene index. XSP10 is very different from the few proteins thus far identified in xylem sap of various plants [5–7,9,10] and represents a new class of small, cysteine‐rich plant‐specific proteins bearing a structural relationship to plant LTPs (Figs. 3 and 4).…”

“…In cucumber xylem sap, several of these have been identified as glycine‐rich proteins, a lectin‐like protein and a chitinase [5–7]. In addition, new proteins appear in xylem sap during development of diseases affecting the vascular system [8–10].…”

A plant natriuretic peptide-like molecule of the pathogen Xanthomonas axonopodis pv. citricauses rapid changes in the proteome of its citrus host

“…It may appear quite counterintuitive that PNPs (including immunoreactant PNPs) are up-regulated in the host in response to pathogen attack [12,66], while at the same time the pathogen gains an advantage by using this molecule to its own advantage. However, it does appear that plant hormone responses are highly complex and triggered and/or modulated by specific ratios of different hormones and signaling molecules.…”

Antigenic Proteins Involved in Occupational Rhinitis and Asthma Caused by Obeche Wood (Triplochiton Scleroxylon)

“…Identification of the 12 kDa protein revealed that it belonged to the gamma-expansin family [29], showing homology with tree-members of this family. Expansins refer to a family of non-enzymatic proteins found in the plant cell wall [30], and which includes small proteins grouped in two large (alpha and beta-expansins) and two small (gamma-, and epsilon- expansins) subfamilies [31].…”