Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2002
Publication Date: N/A
Interpretive Summary: The southern root-knot nematode (RKN) is a serious agricultural pest of cotton. We have identified, cloned and sequenced a novel cDNA from cotton which is correlated with high levels of resistance to RKN. The cDNA encodes a protein of 141 amino acids whose expression is induced specifically in root tissue soon after infection by RKN. Expression of the gene is further localized within the roots to the initial nematode feeding sites. The gene is shown to be a member of a novel multigene family; the translated region of a second clone differs by only 6 of the 141 amino acids. The identification of this novel gene family offers alternative approaches to conventional breeding for utilization of nematode resistant cotton germplasm. Either through its functionality or by use of the tissue specific, nematode inducible promoter, the gene may be used for tailor design of RKN resistance to otherwise susceptible lines of cotton and potentially other RKN sensitive crops.
Technical Abstract: Previous work demonstrated an 14kDa protein was induced in roots of nematode resistant, near-isogenic cotton line (Gossypium hirsutum L.) following inoculation with root-knot nematode (Meloidogyne incognita) (RKN). A root cDNA library was prepared from RKN inoculated root tissue of the resistant cotton line and was screened by PCR using a degenerate primer derived from an internal, eight amino acid fragment of the 14 kDa protein. Three cDNA clones were isolated, sequenced and named MIC-1,2, and 3 (Meloidogyne Induced Cotton-genes). The three clones are very similar encoding proteins of 141 amino acids with estimated pI of 5.4 and molecular mass of 15.3 kDa. Northern analysis using MIC-3 as probe indicated differential expression of the transcript in roots of resistant, RKN inoculated plants in agreement with data showing similar specific induction of the 14 kDa protein. Southern analysis revealed that the MIC clones comprise a multi-gene family containing at least seven members; a RFLP polymorphism between susceptible and resistant near-isogenic lines was noted using EcoRI as the restriction enzyme. Interestingly, the MIC clones show no significant homology to any known sequences in the major gene databases (including EST entries). Overall, these data suggest identification of a unique, root-specific gene family of unknown function. Either through its functionality or by utilization of the putative tissue specific, nematode inducible promoter, the gene(s) may have potential for tailor design of nematode control strategies.