Inducibility by pathogen attack and developmental regulation of the rice Ltp1 gene.
Using a genomic clone encoding a rice lipid transfer protein, LTP1, we analysed the activity of the 5' region of the Ltp1 gene in transgenic rice (Oryza sativa L.) during plant development and under pathogen attack. The -1176/+13, -556/+13 and -284/+13 regions of the promoter were fused upstream from the uidA reporter gene and nos 3' polyadenylation signal, resulting in the pdelta1176Gus, pdelta556Gus and pdelta284Gus constructs which were transferred to rice by microprojectile bombardment. Histochemical and fluorometric GUS assays and in situ detection of uidA transcripts in transgenic homozygous lines harbouring the pdelta1176Gus construct demonstrated that the Ltp1 promoter is preferentially active in aerial vegetative and reproductive organs and that both specificity and level of expression are regulated during organ development. In leaf sheath, GUS activity which is initially strictly localized in the epidermis of growing tissue, becomes restricted to the vascular system in mature tissues. In expanded leaf blade, expression of the uidA gene was restricted to the cutting level suggesting inducibility by wounding. Strong activity was detected in lemma and palea, sterile glumes, and immature anther walls and microspores but not in female reproductive organs. No GUS activity was detected during seed embryo maturation whereas the uidA gene was strongly expressed at early stages of somatic embryogenesis in scutellum tissue. The Ltp1 transcripts were found to strongly accumulate in response to inoculation with the fungal agent of the blast disease, Magnaporthe grisea, in two rice cultivars exhibiting compatible or incompatible host-pathogen interactions. Analysis of pdelta1176Gus leaf samples inoculated with the blast fungus demonstrated that the Ltp1 promoter is induced in all cell types of tissues surrounding the lesion and notably in stomata guard cells. In plants harbouring the Ltp1 promoter deletion construct pdelta556Gus, activity was solely detected in the vascular system of mature leaves whereas no uidA gene expression was observed in pdelta284Gus plants. These observations are consistent with the proposed role of LTP1 in strenghtening of structural barriers and organ protection against mechanical disruption and pathogen attack.
Guiderdoni
Emmanuel
E
BIOTROP and CALIM programmes, Cirad, Centre International de Recherches Agronomiques en coopération pour le Développement, Montpellier, France. Guiderdoni@cirad.fr
Cordero
Maria José
MJ
Vignols
Florence
F
Garcia-Garrido
José Manuel
JM
Lescot
Magali
M
Tharreau
Didier
D
Meynard
Donaldo
D
Ferrière
Nicole
N
Notteghem
Jean-Loup
JL
Delseny
Michel
M
D052179:Antigens, Plant; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D020082:Magnaporthe / Q000254:growth & development*; D008969:Molecular Sequence Data; D009154:Mutation; D012275:Oryza / Q000235:genetics* / Q000254:growth & development / Q000382:microbiology; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000382:microbiology; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion
D052179:Antigens, Plant; D002352:Carrier Proteins; D018744:DNA, Plant; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C511920:lipid transfer proteins, plant; D005966:Glucuronidase