Inheritance of isozyme variation and heterozygosity in Pinus ponderosa

O’Malley, David M.; Allendorf, Fred W.; Blake, G. M.

doi:10.1007/bf00498965

Cited by 93 publications

(28 citation statements)

References 32 publications

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“…Isozyme analysis of megagametophyte tissue revealed a single intensely stained protein band (ADH2), encoded by a single locus (Adh2), as has been reported for several other pines (29)(30)(31)(32). No ADH activity was observed in extracts of aerobically treated roots, but anaerobic treatment resulted in the induction of ADH2 and a more anodal zone of activity (ADH1), for which the genetic control is unknown.…”

Section: Resultssupporting

confidence: 53%

Pinus banksiana has at least seven expressed alcohol dehydrogenase genes in two linked groups

Perry

Furnier

1996

Proc. Natl. Acad. Sci. U.S.A.

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The alcohol dehydrogenase (Adh) gene family is much more complex in Pinus banksiana than in angiosperms, with at least seven expressed genes organized as two tightly linked clusters. Intron number and position are highly conserved between P. banksiana and angiosperms. Unlike angiosperm Adh genes, numerous duplications, as large as 217 bp, were observed within the noncoding regions of P. banksiana Adh genes and may be a common feature of conifer genes. A high frequency of duplication over a wide range of scales may contribute to the large genome size of conifers.It is well-established that nuclear genomes are much larger in conifers than in angiosperms. In conifers, 2C values (where C is the total amount of DNA in a haploid nucleus) typically range from 20 to 50 pg (1), whereas the corresponding values in angiosperms are typically less than 10 pg and often less than 2 pg (2). However, relatively little is known about the organization of these large conifer genomes. While the proportion of repeated DNA is higher than in angiosperms, there is little relationship between total genomic and repetitive DNA (3). Nuclear rDNA repeat units are much longer in conifers (4-6) and Southern blot analyses of pine DNA with cDNA probes often reveal complex band patterns, suggesting larger gene families and͞or larger genes than in angiosperms (7-10).One of the best characterized plant gene families codes for alcohol dehydrogenases (ADH; EC 1.1.1.1), enzymes that play a central role in anaerobic metabolism (11,12). Most angiosperms express two or three ADH isozymes (13) and Southern blots generally display a corresponding level of complexity (14,15). Sequence data are available for Adh genes of a number of angiosperm species, but relatively little is known about this gene family in conifers, with the only published sequences being three partial Pinus radiata Adh cDNAs, likely representing two loci (7). Typically, two to four ADH isozymes are observed in pines (16), but P. radiata Adh cDNA clones hybridize to many fragments of P. radiata and Pinus taeda DNA (7) and many diverse genomic Adh clones were recovered from these species (17). These observations suggest that the Adh gene family is larger in pines than in angiosperms and͞or that pine Adh genes are larger. We characterized Adh genes in Pinus banksiana Lamb. (jack pine) to examine these hypotheses. Also, due to the successful development of segregating PCR-based gene-specific markers, we were able to examine linkage relationships among Adh loci. METHODSIsozyme Analysis. P. banksiana seeds were germinated on distilled (d) H 2 O-moistened filter paper in Petri dishes at room temperature for 8 days, yielding seedling root lengths of 1-2 cm. The germinating seeds were then given either anaerobic treatment (immersed for 20 hr in dH 2 O under filter paper) or aerobic treatment (seeds remained on moist filter paper).Starch gel electrophoresis (18) was used to examine ADH enzyme activity in the haploid megagametophytes and diploid roots of these seedlings.cDNA Cloning and Char...

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Section: Resultssupporting

confidence: 53%

Pinus banksiana has at least seven expressed alcohol dehydrogenase genes in two linked groups

Perry

Furnier

1996

Proc. Natl. Acad. Sci. U.S.A.

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“…Examination of the selfed progeny ofmultiply heterozygous mothers yielded little information due to the low heterozygosity of the mothers and the high mortality among the selfed progeny, but did suggest that PGI2, TPIl, IDH, and PER were not linked in our population. We note that linkage groups are highly conserved in conifers, but we found no reference to linkage among these loci in studies of Pinus taeda (Adams and Joly, 1980;Conkle, 1981), or in other conifers (Guries et al, 1978;O'Malley et al, 1979;Eckert et al, 1981;King and Dancik, 1983;Epperson and Allard, 1984;Strauss and Conkle, 1986). In the absence of evidence to the contrary, we assumed all eight loci to be unlinked.…”

Section: Methodsmentioning

confidence: 81%

“…cesses ofheterozygotes in mature stands are common (O'Malley et al, 1979;Linhart et al, 1981;Cheliak et al, 1985;Plessas and Strauss, 1986;Yeh et al, 1986). Self-pollination appears to be a highly wasteful activity in Pinus taeda, but Franklin (1968), using a comparison of filled seed yields in wind, self, and cross-pollinated seed lots, estimated the natural selfing rate of the maternal trees to be 7% in the upper crown and 34% in the lower crown, not insubstantial rates of self-fertilization, in view ofthe consequences.…”

Section: Mixed Mating Systemmentioning

confidence: 99%

THE IMPACT OF ELECTROPHORETIC GENOTYPE ON LIFE HISTORY TRAITS IN PINUS TAEDA

Bush

Smouse

1991

Evolution

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Abstract.-Reports of positive associations between allozymic heterozygosity and measures of fitness are routine, but it has not been possible to distinguish between the two preeminent explanations of the phenomenon, dominance and overdominance. We tested several ofthe assumptions of these hypotheses in our study of the relationship between electrophoretic genotype and three life history traits in loblolly pines (Pinus taeda L.). Traits examined included the survival and growth of selfed and outcrossed progeny of 45 maternal trees, and maternal fecundity, measured as the number of surviving progeny per mother tree. Inbreeding depression was severe; the relative fitness ofthe selfed progeny was only 8% that of the outcrossed progeny. We found a heterozygote fecundity advantage, which should have resulted in an excess ofrare alleles in the progeny. Instead, there was evidence of severe survival selection against rare alleles in both heterozygous and homozygous forms. The deficit of rare alleles averaged 69 and 50% in the selfed and outcrossed progeny, respectively.The one allele in the sample that we should have suspected ofbeing maintained by overdominance (a PGI2 mid-frequency allele) appeared to be overdominant for outcrossed height growth and probably for fecundity as well. Multiple-locus genotype explained very little of the variation in growth, however, and rather than seeing evidence for overdominance as a force in maintaining most of the observed polymorphism, we were left to explain, in the face of the severe survival selection, why the rare alleles were present at all. Projection of the stand into the future through computer simulation showed how balancing selection acting on differential growth, fecundity, and mortality among genotypes could, over the life of the stand, account for the maintenance of the rare alleles in the population.

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“…Three sets of bands were produced: set I (the most cathodal) comprises the products of one locus, set III (which stains very faintly, if at all) comprises the products of the second locus, and set II consists of their interlocus heterodimers. This pattern also holds for the ADH isozyme of other diploid species in the Poaceae (e.g., Nevo et al, 1979) and even in other families of seed plants (e.g., Brown et al, 1975;O'Malley et al, 1979). Therefore, it is of interest that the ADH isozyme patterns of grain sorghum, Sorghum bicolor (L.) Moench, are different from those of maize, a close relative in the same tribe, the Andropogoneae (Gould, 1968;Doggett, 1976).…”

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confidence: 93%