RESUMO
Polygalacturonase-inhibiting proteins (PGIPs) are leucine-rich repeat (LRR) proteins involved in plant defence. A number of PGIPs have been characterized from dicot species, whereas only a few data are available from monocots. Database searches and genome-specific cloning strategies allowed the identification of four rice (Oryza sativa L.) and two wheat (Triticum aestivum L.) Pgip genes. The rice Pgip genes (Ospgip1, Ospgip2, Ospgip3 and Ospgip4) are distributed over a 30 kbp region of the short arm of chromosome 5, whereas the wheat Pgip genes, Tapgip1 and Tapgip2, are localized on the short arm of chromosome 7B and 7D, respectively. Deduced amino acid sequences show the typical LRR modular organization and a conserved distribution of the eight cysteines at the N- and C-terminal regions. Sequence comparison suggests that monocot and dicot PGIPs form two separate clusters sharing about 40% identity and shows that this value is close to the extent of variability observed within each cluster. Gene-specific RT-PCR and biochemical analyses demonstrate that both Ospgips and Tapgips are expressed in the whole plant or in a tissue-specific manner, and that OsPGIP1, lacking an entire LRR repeat, is an active inhibitor of fungal polygalacturonases. This last finding can contribute to define the molecular features of PG-PGIP interactions and highlights that the genetic events that can generate variability at the Pgip locus are not only limited to substitutions or small insertions/deletions, as so far reported, but can also involve variation in the number of LRRs.
Assuntos
Variação Genética , Oryza/genética , Proteínas de Plantas/genética , Triticum/genética , Sequência de Aminoácidos , Sequência de Bases , Mapeamento Cromossômico , Análise por Conglomerados , Primers do DNA , Perfilação da Expressão Gênica , Dados de Sequência Molecular , Proteínas de Plantas/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Análise de Sequência de DNARESUMO
Polygalacturonase-inhibiting proteins (PGIPs) are plant defence molecules inhibiting the activity of fungal endo-polygalacturonases (endo-PGs). We found that soybean and bean PGIPs inhibited the endo-PG activity produced by the isolate FC-10 of Fusarium moniliforme but not the enzyme activity produced by the isolate PD of F. moniliforme. The bean PGIP proved to be ineffective against all the PG isoforms produced by the PD isolate. Deduced amino acid sequence comparison between PGs from PD, FC-10 and 62264 isolates identified the structural regions of the enzyme possibly related to its resistance to PGIP inhibition. These include one region at the N-terminal portion of the enzyme and a few single amino acid substitutions along the entire sequence, two of which surrounding the active site.
Assuntos
Fusarium/enzimologia , Fusarium/genética , Proteínas de Plantas/metabolismo , Poligalacturonase/genética , Poligalacturonase/metabolismo , Sequência de Aminoácidos , Asparagus/microbiologia , Clonagem Molecular , Dados de Sequência MolecularRESUMO
Polygalacturonase-inhibiting proteins (PGIPs) are extracellular plant inhibitors of fungal endopolygalacturonases (PGs) that belong to the superfamily of Leu-rich repeat proteins. We have characterized the full complement of pgip genes in the bean (Phaseolus vulgaris) genotype BAT93. This comprises four clustered members that span a 50-kb region and, based on their similarity, form two pairs (Pvpgip1/Pvpgip2 and Pvpgip3/Pvpgip4). Characterization of the encoded products revealed both partial redundancy and subfunctionalization against fungal-derived PGs. Notably, the pair PvPGIP3/PvPGIP4 also inhibited PGs of two mirid bugs (Lygus rugulipennis and Adelphocoris lineolatus). Characterization of Pvpgip genes of Pinto bean showed variations limited to single synonymous substitutions or small deletions. A three-amino acid deletion encompassing a residue previously identified as crucial for recognition of PG of Fusarium moniliforme was responsible for the inability of BAT93 PvPGIP2 to inhibit this enzyme. Consistent with the large variations observed in the promoter sequences, reverse transcription-PCR expression analysis revealed that the different family members differentially respond to elicitors, wounding, and salicylic acid. We conclude that both biochemical and regulatory redundancy and subfunctionalization of pgip genes are important for the adaptation of plants to pathogenic fungi and phytophagous insects.
Assuntos
Phaseolus/metabolismo , Doenças das Plantas/microbiologia , Proteínas de Plantas/genética , Sequência de Aminoácidos , Animais , Fungos , Genoma de Planta , Imunidade Inata , Insetos , Dados de Sequência Molecular , Phaseolus/genética , Doenças das Plantas/parasitologia , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Alinhamento de Sequência , Homologia de Sequência de AminoácidosRESUMO
Polygalacturonases (PGs) are produced by fungal pathogens during early plant infection and are believed to be important pathogenicity factors. Polygalacturonase-inhibiting proteins (PGIPs) are plant defense proteins which reduce the hydrolytic activity of endoPGs and favor the accumulation of long-chain oligogalacturonides (OGs) which are elicitors of a variety of defense responses. PGIPs belong to the superfamily of leucine reach repeat (LRR) proteins which also include the products of several plant resistance genes. A number of evidence demonstrates that PGIPs efficiently inhibit fungal invasion.