|CHEN, Z. - LSU Agcenter
|Wei, Qijian - Mei Mei
|RARUANG, Y - LSU Agcenter
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2015
Publication Date: 3/20/2016
Citation: Chen, Z.Y., Warburton, M.L., Hawkins, L.K., Wei, Q., Brown, R.L., Bhatnagar, D., Raruang, Y. 2016. Production of the 14 kDa trypsin inhibitor protein is important for maize resistance against Aspergillus flavus infection/aflatoxin. World Mycotoxin Journal. 9(2):215-228.
Interpretive Summary: Maize is susceptible to Aspergillus flavus Link, a fungus which produces a toxin (aflatoxin) that is dangerous to humans and animals who ingest it. A trypsin inhibitor (TI) protein from maize has been found to slow the growth of A. flavus in past studies. This article shows two new lines of evidence of a role for the TI protein in fungal resistance. The gene encoding TI protein was silenced using RNAi technology, and resulting lines produced significantly less TI protein. They were also contained more aflatoxin than non-transgenic maize lines. Genetic mapping of the gene encoding the TI protein was also done in maize populations containing different forms of the TI gene. Lines containing one form also contained lower amounts of aflatoxin than did lines containing another form, and this may be attributable to the TI gene.
Technical Abstract: Maize (Zea mays L.) is one of the major crops susceptible to Aspergillus flavus Link ex. Fries infection and subsequent aflatoxin contamination. Previous studies found the expression of an antifungal 14 kDa trypsin inhibitor (TI) was associated with maize aflatoxin resistance. To further investigate whether the TI plays any direct role in resistance, a TI gene silencing vector was constructed and transformed into maize. Mature kernels were produced from 66 transgenic lines representing 18 independent events. Twenty lines confirmed to contain 10 independent transformation events were further evaluated. Compared to the non-silenced control, significant reductions in TI transcript abundance were observed at the RNA level (63 to 88%) in seedling leaf tissue of 5 of the 12 lines, and at the protein level (39-85%) in mature kernels in 7 of the 12 lines. In addition, the kernels of six of the 7 lines with significant TI reduction at the protein level contained higher aflatoxin levels compared to negative controls. To further confirm a possible role of the TI protein in field resistance of aflatoxin accumulation, DNA sequence polymorphisms from within the gene or linked SSRs were tested in four QTL mapping populations for QTL effect, and three QTL possibly caused by the TI protein encoding gene were found. Sequence polymorphisms were also tested for association to aflatoxin levels in an association mapping panel, and three SNPs were weakly associated with aflatoxin accumulation (p < 0.01). This study demonstrated the importance of TI expression in maize resistance to A. flavus infection and/or aflatoxin production.