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

Abstract

The alcohol dehydrogenase (Adh) gene family is much more complex in Pinus banksiana than in angio-sperms, 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.

Figure 1

Schematic representation of four P. banksiana Adh genes. Numbered boxes represent exons and lines represent introns and 3′ UTRs. Arrows delineate 10- (a) and 43-bp (b) direct repeats in AdhC2, 141-bp (c) inverted repeat in AdhC3 and AdhC5, 65- (d) and 49-bp (e) direct repeats in AdhC5, and 86- (f), 106- (g), 17- (h), 40- (i), 21- (j), 12- (k), 217- (l), and 11- (m) bp direct repeats in AdhC6. Gene lengths are estimated from the presumed beginning of the initiation codon through the termination codon.

Figure 3

Phylogeny of Adh cDNA sequences inferred by the neighbor-joining method (26) from Jukes–Cantor distances (27) and rooted using human Adh χ (GenBank accession no. M30471M30471). Numbers represent the relative support for groupings based upon 1000 bootstrap trees and the scale bar represents 0.1 substitutions per site. The angiosperm genes included are Arabidopsis thaliana Adh (Ath; GenBank accession no. M12196M12196); Fragaria ananassa Adh (Fan; X15588X15588); Hordeum vulgare Adh1 (Hvu1; X07774X07774), Adh2 (Hvu2; X12733X12733), and Adh3 (Hvu3; X12734X12734); Lycopersicon esculentum Adh2 (Les2; M86724M86724); Malus domestica Adh (Mdo; Z48234Z48234); Nicotiana tabacum Adh (Nta; X81853X81853); Oryza sativa Adh1 (Osa1; X16296X16296) and Adh2 (Osa2; X16297X16297); Phaseolus acutifolius Adh1-F (Pac1; Z23170Z23170); Pennisetum americanum Adh1-S (Pam1; X16547X16547); Petunia hybrida Adh1 (Phy1; X54106X54106); Pisum sativum Adh1 (Psa1; X06281X06281); Solanum tuberosum Adh (Stu; X53242X53242); Trifolium repens Adh1 (Tre1; X14826X14826); Triticum aestivum Adh (Tae; ref. 37); and Zea mays Adh1-S (Zma1; X04049X04049) and Adh2 (Zma2; X01965X01965).

Figure 2

Joint segregation of Adh2 allozymes and a PCR-based marker of AdhC7. (A) Adh2 allozymes in 10 haploid megagametophytes of a single tree as detected using starch gel electrophoresis and enzyme staining. (B) PCR amplification products of AdhC7 from the same set of 10 megagametophytes revealed by agarose gel electrophoresis and ethidium bromide staining. Size markers shown in the right hand lane are the 1636-, 1018-, and 506-bp fragments of a 1-kb DNA ladder (GIBCO/BRL).