Abstract
Maize (Zea mays L.) lipoxygenases (ZmLOXs) are well recognized as important players in plant defense against pathogens, especially in cross kingdom lipid communication with pathogenic fungi. This study is among the first to investigate genetic diversity at important gene paralogs ZmLOX4 and ZmLOX5. Sequencing of these genes in 400 diverse maize lines showed little genetic diversity and low linkage disequilibrium in the two genes. Importantly, we identified one inbred line in which ZmLOX5 has a disrupted open reading frame, a line missing ZmLOX5, and five lines with a duplication of ZmLOX5. Tajima's D test suggests that both ZmLOX4 and ZmLOX5 have been under neutral selection. Further investigation of haplotype data revealed that within the ZmLOX family members only ZmLOX12, a monocot specific ZmLOX, showed strong linkage disequilibrium that extends further than expected in maize. Linkage disequilibrium patterns at these loci of interest are crucial for future candidate gene association mapping studies. ZmLOX4 and ZmLOX5 mutations and copy number variants are under further investigation for crop improvement.
Highlights
Lipids and their oxidized derivatives, oxylipins, play a role in plant reaction to stress and plant-microbe interactions [1,2]
The genic structure and polymorphism of ZmLOX4 and ZmLOX5. Both ZmLOX4 and ZmLOX5 have the same genic architecture consisting of 9 exons and 8 introns
PCR amplification of ZmLOX4 and ZmLOX5 specific products was difficult even on the small sample size of lines used for primer design and genotyping, and proved even more difficult when genetic diversity was increased across the lines included in the association panels
Summary
Lipids and their oxidized derivatives, oxylipins, play a role in plant reaction to stress and plant-microbe interactions [1,2]. Lipid mediated interactions between pathogens and plants have gained increased attention, as a disruption of plant-microbe communication could provide an avenue for resistance to diseases [3]. While quantitative resistance to A. flavus has been identified and selected for in maize, no major genes for resistance have been identified and the problem is complex [7]. The regulation of mycotoxin production in fungi is partially mediated by genes belonging to the lipoxygenase (LOX) family [8]. LOX genes are found in plant, fungal and animal kingdoms, and LOX mediated cross-kingdom interactions are hypothesized to be involved in the susceptibility of plants to fungal invasion and subsequent mycotoxin production [2]. The specific molecular signals from plants or fungi that trigger mycotoxin production are poorly understood
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