Dr. Hugo K. Dooner is a Distinguished Professor in the Plant Biology Department at Rutgers and a Principal Investigator in the Waksman Institute. He was elected to the National Academy of Sciences in 2007 for his studies on the contribution of transposable elements and recombination to the genetic diversity of maize. He discovered extreme haplotype variation among inbred maize lines and developed heterologous transposon tagging to isolate genes of agricultural importance. His lab studies transposon architecture and interactions to elucidate gene function and to create a more efficient resource for reverse genetics.
His lab performs studies on genome structure, homologous meiotic recombination, and functional genomics in maize. They have observed that rather than adhering to a rigid plan, the genomes of many organisms, like maize and humans, comprise mobile, gene-coding DNA elements. Dooner sees these as small islands of gene-coding regions in a vast sea of highly repeated sequences. In maize, these "islands" shift positions along or between chromosomes, yet remain intact and functional in the process. With chromosomal exchanges limited to the sequences between gene-coding regions, genes remain unscathed in different neighborhoods. The result is functional genes in multiple neighborhoods, concluding that this picture is one of a protective evolutionary adaptation.
Research in the Dooner Lab Focuses on Three Main Areas:
Transposons are the main consitutents of the maize genome. We study their structures and interactions and use them as genetic tools to elucidate the function of genes. We have identified several new genetically active transposons, including Jittery, Mx, and TED, which are new autonomous members of the Mutator and hAT superfamilies. Maize appears to have several noninteracting elements in each superfamily, suggesting that new transposon specificities have arisen frequently. In our functional genomics project, we have generated an Ac insertion library which yielded many new interesting phenotypes, such as defective pollen grains with corkscrew pollen tube and seedings unable to produce volatile chemicals to defend themselves against insects. We are currently optimizing the use of Ac-Ds transposons as gene-searching engines in maize. We are developing a set of transgenic lines carrying a uniquely marked Ds element which should integrate at multiple locations in the genome and greatly facilitate the isolation of the interrupted gene and generating thousands of sequence-indexed single gene knockouts for use by the maize community.
2. Genome variability
Maize is the most variable plant species known. This variability manifests itself at all levels, ranging from variations in plant shape to polymorphisms in restriction enzyme sites. We recently discovered that allelic regions of the genome can vary by as much as 70% of their DNA, including the presence or absence of certain genes. This finding may help to explain the phenomena of hybrid vigor and inbreeding depression. We are presently characterizing two specific regions in the genome of different inbreds, land races, and wild relatives of maize in order to further document the extent of this variability.
3. Homologous recombination
We have previously found that meitoic recombination in maize is restricted to genes, which comprise only 5% or less of the genome. We continue to use the bronze locus of maize, a uniquely advantageous system, to attempt to obtain answers to basic questions regarding the process of homologous meiotic recombination in plants. A main question that we are addressing is the effect of sequence diversity on the outcome of recombination events in maize. Most recombination events between pairs of highly polymorphic maize alleles are crossovers. However, intragenic recombination events not associated with flanking marker exchange, corresponding to noncrossover (NCO) gene conversions, predominate between alleles derived from the same progenitor. In these dimorphic heterozygotes, the two alleles differ only at the two mutant sites between which recombination is being measured. We have recently found that NCO gene conversion at the bz locus exhibits a striking polarity, with sites located within 150 bp of the start and stop codons converting more frequently than sites located in the middle of the gene.