Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/30/2012
Publication Date: 8/12/2012
Citation: Wubben, M., Callahan, F.E., Jenkins, J.N., Velten, J.P. 2012. Over-expression of MIC3 reduces cotton susceptibility to root-knot nematode [abstract]. Society of Nematologists Conference. CD-ROM.
Technical Abstract: While the inheritance of root-knot nematode (Meloidogyne incognita; RKN) resistance in cotton (Gossypium hirsutum) has been the focus of much research, the mechanism of the resistance at the molecular level remains largely unknown. To date, increased transcript and protein levels of MIC3 (Meloidogyne Induced Cotton3) in galls of resistant plants remains the only example of a gene whose expression is correlated with the onset of RKN resistance in cotton. MIC3 represents a large gene family in cotton that encode proteins approximately 14 kDa in size that lack similarity with known proteins and do not contain any known domains or motifs; furthermore, MIC3 appears to be a cotton-specific gene with no homologous sequences being identified outside the genus Gossypium. In this report, we further validate the correlation between MIC3 expression and RKN resistance via overexpression of MIC3 in the RKN-susceptible line Coker312. A MIC3 overexpression cassette driven by the CaMV35S promoter was constructed using the binary vector pBI121. Transgenic cotton lines harboring this cassette were created using Agrobacterium tumefaciens. Five (5) homozygous T2 lines were identified that showed elevated MIC3 transcript and protein levels in roots and leaves compared to non-transgenic controls. For the RKN assays, data from two independent experiments showed that both high and low levels of MIC3 overexpression affected RKN egg production but not RKN-induced root galling. We found that the transgenic line 11-1-1Top, which showed 14.7-fold higher MIC3 transcript in uninfected roots compared to the non-transgenic control, supported 70% fewer RKN eggs/plant compared to the susceptible control Coker312. In contrast, the transgenic line 14-11-1Top, which showed the lowest level of MIC3 overexpression of the five homozygous lines, reduced RKN eggs/plant by only 35% compared to Coker312. None of the transgenic lines showed gall index scores that were significantly different from the susceptible controls. In contrast to RKN, MIC3 overexpression did not affect cotton susceptibility to neither the reniform nematode (Rotylenchulus reniformis) nor the foliar pathogen Heliothis zea.