Biomedical subjects

M Purugganan

Publications and source records attributed to M Purugganan.

6 recordsLinked to original sources

PubMed2005

The molecular population genetics of the Tomato spotted wilt virus (TSWV) genome.

RNA viruses are characterized by high genetic variability resulting in rapid adaptation to new or resistant hosts. Research for plant RNA virus genetic structure and its variability has been relatively scarce compared to abundant research done for human and animal RNA viruses. Here, we utilized a molecular population genetic framework to characterize the evolution of a highly pathogenic plant RNA virus [Tomato spotted wilt virus (TSWV), Tospovirus, Bunyaviridae]. Data from genes encoding five viral proteins were used for phylogenetic analysis, and for estimation of population parameters, subpopulation differentiation, recombination, divergence between Tospovirus species, and selective constraints on the TSWV genome. Our analysis has defined the geographical structure of TSWV, attributed possibly to founder effects. Also, we identify positive selection favouring divergence between Tospovirus species. At the species level, purifying selection has acted to preserve protein function, although certain amino acids appear to be under positive selection. This analysis provides demonstration of population structuring and species-wide population expansions in a multisegmented plant RNA virus, using sequence-based molecular population genetic analyses. It also identifies specific amino acid sites subject to selection within Bunyaviridae and estimates the level of genetic heterogeneity of a highly pathogenic plant RNA virus. The study of the variability of TSWV populations lays the foundation in the development of strategies for the control of other viral diseases in floral crops.

Base Sequence↗

PubMed2000

Interspecific evolution in plant microsatellite structure.

Several intragenically linked microsatellites have been identified in the floral regulatory genes A. sandwicense APETALA1 (ASAP1) and A. sandwicense APETALA3/TM6 (ASAP3/TM6) in 17 species of the Hawaiian and North American Madiinae (Asteraceae). Thirty-nine microsatellite loci were observed in the introns of these two genes, suggesting that they are hotspots for microsatellite formation. The sequences of four of these microsatellites were mapped onto the phylogenies of these floral regulatory genes, and the structural evolution of these repeat loci was traced. Both nucleotide substitutions and insertion/deletion mutations may be responsible for the formation of perfect microsatellites from imperfect repeat regions (and vice versa).

Carrier Proteins↗

PubMed2000

Quantitative trait loci for floral morphology in Arabidopsis thaliana.

A central question in biology is how genes control the expression of quantitative variation. We used statistical methods to estimate genetic variation in eight Arabidopsis thaliana floral characters (fresh flower mass, petal length, petal width, sepal length, sepal width, long stamen length, short stamen length, and pistil length) in a cosmopolitan sample of 15 ecotypes. In addition, we used genome-wide quantitative trait locus (QTL) mapping to evaluate the genetic basis of variation in these same traits in the Landsberg erecta x Columbia recombinant inbred line population. There was significant genetic variation for all traits in both the sample of naturally occurring ecotypes and in the Ler x Col recombinant inbred line population. In addition, broad-sense genetic correlations among the traits were positive and high. A composite interval mapping (CIM) analysis detected 18 significant QTL affecting at least one floral character. Eleven QTL were associated with several floral traits, supporting either pleiotropy or tight linkage as major determinants of flower morphological integration. We propose several candidate genes that may underlie these QTL on the basis of positional information and functional arguments. Genome-wide QTL mapping is a promising tool for the discovery of candidate genes controlling morphological development, the detection of novel phenotypic effects for known genes, and in generating a more complete understanding of the genetic basis of floral development.

Arabidopsis↗

PubMed1992

The splicing of transposable elements and its role in intron evolution.

Recent studies have demonstrated that transposable elements in maize and Drosophila are spliced from pre-mRNA. These transposable element introns represent the first examples of recent addition of introns into nuclear genes. The eight reported examples of transposable element splicing include members of the maize Ac/Ds and Spm/dSpm and the Drosophila P and 412 element families. The details of the splicing of these transposable elements and their relevance to models of intron origin are discussed.

Animals↗

PubMed1992

Alternative splicing induced by insertion of retrotransposons into the maize waxy gene.

The molecular basis for the low level expression of three alleles of the maize waxy (Wx) gene has been described. Each allele contains a retrotransposon in intron sequences. These insertions represent previously undescribed elements, and their association with three wx alleles indicates that retrotransposon elements are important agents of spontaneous mutation in maize. For each allele, element sequences are spliced from pre-mRNA with the surrounding intron even though the insertions increase intron length by approximately 40- to 60-fold. In addition, despite differences in element sequences, insertion sites, and relative orientations, each element disrupts long-range splice site recognition leading to novel Wx transcripts where exons both upstream and downstream of the insertion site are skipped. The expression of wx alleles with large insertions in introns provides support for studies that indicate that the primary cis requirement for maize introns is the splice donor and acceptor sites.

Alternative Splicing↗

PubMed1990

Filler DNA is associated with spontaneous deletions in maize.

We have determined the structure of five spontaneous deletions within the maize waxy (Wx) gene. Of these, four were found in spontaneous wx mutants (wx-B, wx-B1, wx-B6, wx-C4) and include exon sequences; the fifth is restricted to an intron and represents a restriction fragment length polymorphism of a nonmutant allele (Wx-W23). The deletions, which range in size from 60 to 980 base pairs (bp), cluster in a G+C-rich region of approximately 1000 bp that is capable of forming stable secondary structures. Most striking is our finding that all of the alleles have DNA insertions (filler DNA) of 1-131 bp between the deletion endpoints. For three of the five deletions, the filler DNA and sequences at the deletion termini appear to be derived from sequences near one deletion endpoint. A previously reported spontaneous deletion of the maize bronze gene (bz-R) also contains filler DNA. The association of filler DNA with maize deletion endpoints contrasts dramatically with the rarity of similar events in animal germ-line and bacterial mutations.

Base Sequence↗