GENETIC AND GENOMIC APPROACHES TO IMPROVE PEANUT AND CORN RESISTANCE TO DISEASE AND AFLATOXIN CONTAMINATION
Location: Crop Protection and Management Research
Title: Root morphology and gene expression analysis in response to drought stress in maize (Zea mays)
Submitted to: Plant Molecular Biology Reporter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 22, 2011
Publication Date: March 16, 2012
Citation: Jiang, T., Fountain, J., Davis, G., Kemerait, R., Scully, B.T., Lee, R.D., Guo, B. 2012. Root morphology and gene expression analysis in response to drought stress in maize (Zea mays). Plant Molecular Biology Reporter. 30:360-369.
Interpretive Summary: Aflatoxin contamination is considered one of the most serious food safety issues concerning human health worldwide. Research experiments have demonstrated that higher levels of plant defense- or stress-related chemicals occurred in corn seeds of resistant varieties compared with susceptible ones, suggesting that field condition (drought stress or no stress) influences the production of these chemical compounds differently in different corn varieties. Experiments were conducted to investigate variations in morphological, physiological and gene expression responses in the leaves, roots, and developing kernels of two inbred lines, Lo964 and Lo1016, under drought stress conditions. The results revealed that Lo964 had a strong lateral root system, a higher root/shoot ratio, and a higher production of ABA in comparison with Lo1016 under drought. Gene expression was also investigated for MIPS, ZmPR10 and ZmFer1. Further study is needed to confirm if Lo964 has reduced aflatoxin contamination associated with the drought tolerance in order to utilize the resistant trait in breeding.
Water-deficit stress tolerance is a complex trait, and water deficit results in various physiological and chemical changes in maize (Zea mays L.) and exacerbates preharvest aflatoxin contamination. The objective of this study was to characterize the variations in morphology, physiology and gene expression in two contrasting inbred lines, Lo964 and Lo1016, in order to understand the differences in response to water-deficit stress. The results revealed that Lo964 was less sensitive to water-deficit stress, and had a strong lateral root system and a higher root/shoot ratio in comparison to Lo1016, sensitive to water stress. In response to water-deficit stress by comparing stressed versus watered conditions, ABA syntheses were increased in leaves, roots and kernels of both Lo964 and Lo1016, but by different magnitudes. In Lo964, ABA levels were increased by the multiples of 18.4 and 10.5 in the leaves, 2.7 and 7.8 in the roots at seedling and grain-filling stages, respectively. In contrast, in Lo1016, ABA levels were increased by the multiples of 5.8 and 2.1 in the leaves, 1.8 and 4.3 in the roots of seedling and grain-filling stages, respectively. However, in the kernels, ABA levels were increased in all samples in both lines, but at 20 days after pollination (DAP), Lo964 increased by 19.5% and Lo1016 by 85.1% in response to water stress. IAA was undetectable in the leaves and roots of either genotype regardless of treatments, but increases of 58% and 8% in IAA concentration were observed in 20 DAP kernels, in response to water-deficit stress, respectively. The expression of the MIPS was up-regulated 7 fold in leaf tissues of Lo964 compared to Lo1016 at watered conditions, but decreased significantly to similar levels in both genotypes at water-deficit conditions. ZmPR10 and ZmFer1 expressions tended to up-regulate although ZmPR10 was expressed higher in root tissue while ZmFer1 was expressed higher in leaf tissue. These data support previous observation that Lo964 is more tolerant to water-deficit stress than Lo1016. Further study is needed to confirm if Lo964 has reduced aflatoxin contamination associated with the drought tolerance in the field in order to utilize the resistant trait in breeding.