Induction of the Hahsp17.7G4 promoter by root-knot nematodes: involvement of heat-shock elements in promoter activity in giant cells.
Root-knot nematodes feed from specialized giant cells induced in the plants that they parasitize. We found that the promoter of the Hahsp17.7G4 gene, which encodes a small heat-shock protein involved in embryogenesis and stress responses, directed GUS expression in tobacco galls induced by the root-knot nematode Meloidogyne incognita. In roots containing a GUS reporter fusion to the Hahsp17.7G4 promoter, 10% of the galls stained for GUS expression 1 to 3 days after infection and the fraction stained increased to 60 to 80% 17 to 20 days after infection. A DNA fragment from -83 to +163, which contains heat-shock element (HSE) core sequences, is sufficient to support a promoter activity largely restricted to giant cells within the galls. Two-point mutations in HSE cores, previously reported to abolish the heat-shock response and to strongly reduce the embryogenesis response of the same promoter, did not reduce expression in giant cells. This suggests a distinct regulation of the promoter by nematodes. However, additional point mutations located at positions crucial for binding of heat-shock transcription factors (HSFs) caused a severe decrease in the nematode response. These results demonstrate that HSEs are involved in the promoter activation in giant cells and suggest that HSFs may mediate this response.
Escobar
Carolina
C
Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Campus de la Real Fábrica de Armas, E-45071 Toledo, Spain. carolina.escobar@uclm.es
Barcala
Marta
M
Portillo
Mary
M
Almoguera
Concepción
C
Jordano
Juan
J
Fenoll
Carmen
C
D000818:Animals; D001483:Base Sequence; D018744:DNA, Plant; D006360:Heat-Shock Proteins / Q000235:genetics*; D009348:Nematoda / Q000235:genetics*; D018517:Plant Roots / Q000166:cytology / Q000469:parasitology*; D030821:Plants, Genetically Modified / Q000166:cytology / Q000469:parasitology; D011401:Promoter Regions, Genetic; D014026:Nicotiana / Q000166:cytology / Q000469:parasitology*
D018744:DNA, Plant; D006360:Heat-Shock Proteins