A CC-NBS-LRR type gene GHNTR1 confers resistance to southern root-knot nematode in Nicotiana.benthamiana and Nicotiana.tabacum

摘要

Root-knot nematodes are obligate parasites that invade the roots of agricultural plants and induce the formation of specialized feeding structures, especially races 3 and 4 of the southern root-knot nematode. However, not much is known about the defense mechanisms of plants against the invasion of M. incognita race 1. In this study, we characterized and performed functional analysis of the CC-NBS-LRR domain gene, GHNTR1. Using the GHNTR1 promoter to drive the GUS marker gene, we found that GUS expression was high in the roots and shoots of seedlings, four leaves stages, and mature stages. When GHNTR1 was transiently expressed in Nicotiana. benthamiana and Nicotiana. tabacum, necrosis was observed in the leaves and detectable amounts of H2O2 had accumulated when compared to the control plants. Stable transformation of N. benthamiana with the GHNTR1 gene using Agrobacterium induced the expression of defense marker genes PR1, PR2, LOX, and ERF1. In addition, the transgenic N. benthamiana and N. tabacum plants exhibited higher resistance to M. incognita infection. When transgenic N. tabacum were challenged with M. incognita, callose deposition and peroxide accumulation were observed in the roots by aniline-blue and DAB staining, respectively. Sequencing and bioinformatic analysis of small RNA revealed 48 miRNAs were up-regulated and 32 miRNAs were down-regulated. Further, 345 genes were predicted as targets of miRNAs and these included genes that are involved in cell death, death, and stress response. Thus, GHNTR1 is the first gene isolated from cotton that confers resistance against M. incognita and it induced a series of hypersensitive responses in transgenic tobacco. These findings improve our understanding of the molecular mechanisms of the response of upland cotton to M. incognita infection.