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Identification of defensin-encoding genes of Picea glauca: characterization of PgD5, a conserved spruce defensin with strong antifungal activity.

ABSTRACT: BACKGROUND: Plant defensins represent a major innate immune protein superfamily that displays strong inhibitory effects on filamentous fungi. The total number of plant defensins in a conifer species is unknown since there are no sequenced conifer genomes published, however the genomes of several angiosperm species provide an insight on the diversity of plant defensins. Here we report the identification of five new defensin-encoding genes from the Picea glauca genome and the characterization of two of their gene products, named PgD5 and endopiceasin. RESULTS: Screening of a P. glauca EST database with sequences of known plant defensins identified four genes with homology to the known P. glauca defensin PgD1, which were designated PgD2-5. Whereas in the mature PgD2-4 only 7-9 amino acids differed from PgD1, PgD5 had only 64% sequence identity. PgD5 was amplified from P. glauca genomic DNA by PCR. It codes for a precursor of 77-amino acid that is fully conserved within the Picea genus and has similarity to plant defensins. Recombinant PgD5, produced in Escherichia coli, had a molecular mass of 5.721 kDa, as determined by mass spectrometry. The PgD5 peptide exhibited strong antifungal activity against several phytopathogens without any effect on the morphology of the treated fungal hyphae, but strongly inhibited hyphal elongation. A SYTOX uptake assay suggested that the inhibitory activity of PgD5 could be associated with altering the permeability of the fungal membranes. Another completely unrelated defensin gene was identified in the EST library and named endopiceasin. Its gene codes for a 6-cysteine peptide that shares high similarity with the fungal defensin plectasin. CONCLUSIONS: Screening of a P. glauca EST database resulted in the identification of five new defensin-encoding genes. PgD5 codes for a plant defensin that displays non-morphogenic antifungal activity against the phytopathogens tested, probably by altering membrane permeability. PgD5 has potential for application in the plant biotechnology sector. Endopiceasin appears to derive from an endo- or epiphytic fungal strain rather than from the plant itself.

SUBMITTER: Picart P

PROVIDER: S-EPMC3502332 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Identification of defensin-encoding genes of Picea glauca: characterization of PgD5, a conserved spruce defensin with strong antifungal activity.

Picart Pere P Pirttilä Anna Maria AM Raventos Dora D Kristensen Hans-Henrik HH Sahl Hans-Georg HG

BMC plant biology 20121005

<h4>Background</h4>Plant defensins represent a major innate immune protein superfamily that displays strong inhibitory effects on filamentous fungi. The total number of plant defensins in a conifer species is unknown since there are no sequenced conifer genomes published, however the genomes of several angiosperm species provide an insight on the diversity of plant defensins. Here we report the identification of five new defensin-encoding genes from the Picea glauca genome and the characterizati ...[more]

PMID: 23035776

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Project description:Tree improvement programs select genotypes for faster growth, at both early and late stages, to increase yields over unimproved material, and the improvement is frequently attributed to genetic control in growth parameters among genotypes. Underutilized genetic variability among genotypes also has the potential to ensure future gains are possible. However, the genetic variation in growth, physiology and hormone control among genotypes generated from different breeding strategies has not been well characterized in conifers. We assessed growth, biomass, gas exchange, gene expression and hormone levels in white spruce seedlings obtained from three different breeding strategies (controlled crosses, polymix pollination, open pollination) using parents grafted into a clonal seed orchard in Alberta, Canada. A pedigree-based best linear unbiased prediction (ABLUP) mixed model was implemented to quantify variability and narrow-sense heritability for target traits and the levels of several hormones and expression of gibberellin-related genes in apical internodes were also determined. Over the first 2-years of development, the estimated heritabilities for height, volume, total dry biomass, above ground dry biomass, root:shoot ratio and root length, varied between 0.10 and 0.21, with height having the highest value. The ABLUP values showed large genetic variability in growth and physiology traits both between families from different breeding strategies, and within families. The principal component analysis showed that developmental and hormonal traits explained 44.2% and 29.4% of the total phenotypic variation between the three different breeding strategies and two growth groups. In general, controlled crosses from the fast growth group showed the best apical growth, with more accumulation of indole-3-acetic acid, abscisic acid, phaseic acid, and a 4-fold greater gene expression of PgGA3ox1 in genotypes from controlled crosses versus those from open pollination, but in some cases, open-pollination from the fast and slow growth groups showed the best root development, higher water use efficiency (iWUE and δ13C) and more accumulation of zeatin and isopentenyladenosine. In conclusion, tree domestication can lead to trade-offs between growth, carbon allocation, photosynthesis, hormone levels and gene expression, and we encourage the use of this phenotypic variation identified in improved and unimproved trees to advance white spruce tree improvement programs.

Dataset Information

Identification of defensin-encoding genes of Picea glauca: characterization of PgD5, a conserved spruce defensin with strong antifungal activity.

Publications

Identification of defensin-encoding genes of Picea glauca: characterization of PgD5, a conserved spruce defensin with strong antifungal activity.

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