NtKTI1, a Kunitz trypsin inhibitor with antifungal activity from Nicotiana tabacum, plays an important role in tobacco's defense response.
A cDNA library from tobacco inoculated with Rhizoctonia solani was constructed, and several cDNA fragments were identified by differential hybridization screening. One cDNA clone that was dramatically repressed, NtKTI1, was confirmed as a member of the Kunitz plant proteinase inhibitor family. RT-PCR analysis revealed that NtKTI1 was constitutively expressed throughout the whole plant and preferentially expressed in the roots and stems. Furthermore, RT-PCR analysis showed that NtKTI1 expression was repressed after R. solani inoculation, mechanical wounding and salicylic acid treatment, but was unaffected by methyl jasmonate, abscisic acid and NaCl treatment. In vitro assays showed that NtKTI1 exerted prominent antifungal activity towards R. solani and moderate antifungal activity against Rhizopus nigricans and Phytophthora parasitica var. nicotianae. Bioassays of transgenic tobacco demonstrated that overexpression of NtKTI1 enhanced significantly the resistance of tobacco against R. solani, and the antisense lines exhibited higher susceptibility than control lines towards the phytopathogen. Taken together, these studies suggest that NtKTI1 may be a functional Kunitz trypsin inhibitor with antifungal activity against several important phytopathogens in the tobacco defense response.
Huang
Hao
H
State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong, China.
Qi
Sheng-Dong
SD
Qi
Fang
F
Wu
Chang-Ai
CA
Yang
Guo-Dong
GD
Zheng
Cheng-Chao
CC
D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000494:pharmacology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D018517:Plant Roots / Q000201:enzymology; D018547:Plant Stems / Q000201:enzymology; D030821:Plants, Genetically Modified / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012232:Rhizoctonia / Q000472:pathogenicity*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000201:enzymology / Q000235:genetics* / Q000382:microbiology; D014361:Trypsin Inhibitors / Q000235:genetics / Q000494:pharmacology
D000935:Antifungal Agents; D018076:DNA, Complementary; D018744:DNA, Plant; D014361:Trypsin Inhibitors; C092375:NtK-1 protein, Nicotiana tabacum; D017346:Protein Serine-Threonine Kinases