Rapid increases in global temperature are likely to impose strong directional selection on many plant populations, which must therefore adapt if they are to survive. Within populations, microgeographic genetic differentiation of individuals with respect to climate suggests that some populations may adapt to changing temperatures in the short-term through rapid changes in gene frequency. We used a genome scan to identify temperature-related adaptive differentiation of individuals of the tree species Fagus sylvatica. By combining molecular marker and dendrochronological data we assessed spatial and temporal variation in gene frequency at the locus identified as being under selection. We show that gene frequency at this locus varies predictably with temperature. The probability of the presence of the dominant marker allele shows a declining trend over the latter half of the 20th century, in parallel with rising temperatures in the region. Our results show that F. sylvatica populations may show some capacity for an in situ adaptive response to climate change. However as reported ongoing distributional changes demonstrate, this response is not enough to allow all populations of this species to persist in all of their current locations.

Rapid climate change will impose strong directional selection pressures on natural plant populations. Climate-linked genetic variation in natural populations indicates that an evolutionary response is possible. We investigated such a response by comparing individuals subjected to elevated drought and warming treatments with individuals establishing in an unmanipulated climate within the same population. We report that reduction in seedling establishment in response to climate manipulations is nonrandom and results from the selection pressure imposed by artificially warmed and droughted conditions. When compared against control samples, high single-locus genetic divergence occurred in drought and warming treatment samples, with genetic differentiation up to 37 times higher than background (mean neutral locus) genetic differentiation. These loci violate assumptions of selective neutrality, indicating the signature of natural selection by drought. Our results demonstrate that rapid evolution in response to climate change may be widespread in natural populations, based on genetic variation already present within the population.

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For the first time, numerous sequences of Copia and Gypsy retrotransposons from the Cucumis melo genome have been obtained and analyzed. Phylogenetic analyses of sequences of both types of long terminal repeat (LTR) retrotransposons were carried out. The melon genome contains approximately 20,000 Gypsy and 6,800 Copia elements, comprising about 26% of its total size. Starting from a retrotransposon fragment, we have cloned and characterized an entire melon retrotransposon, named Reme1, which is 5,149 bp long. Reme1 belongs to the Superfamily Copia retrotransposons by its protein domain order and sequence similarity to other Copia elements of dicotyledons. The haploid genome of melon (var. "Piel de Sapo") contains about 120 copies of Reme1. Several copies of Reme1 are transcriptionally active, although at low levels, in melon leaves as analyzed by reverse-transcription PCR (RT-PCR) and sequencing. However, the transcript pool is considerably increased when melon leaves are treated with UV light, as has been seen for various retroelements in many organisms. The cDNAs of Reme1 transcripts showed less diversity than do Reme1 genomic sequences, suggesting that a subfamily of these elements is differentially responsive to UV.

MATERIALS AND METHODSVirus Isolation. CaMV, strain CM4-184 (16) was propagated in turnips (Brassica rapa, Just Right). Viral particles free of inclusion bodies were isolated as described (17).Purification of Viral Capsid Proteins and Antisera Production. CaMV particles were subjected to preparative NaDod-S04/PAGE (46). After electrophoresis the gel was soaked in 0.5 M KCl at 40C, and the opaque gel bands were excised and washed three times with 0.5 M NaCl. Pieces of gel (1 cm3 Phosphoamino Acid Analysis. Analysis was as described (20). RESULTSCaMV Structural Proteins and in Vitro Phosphorylation. The NaDodSO4/PAGE analysis of CaMV particles reveals a complex pattern of major and minor protein bands (21,22). The pattern shown in Fig. 1, lane 1, is obtained only when fresh virus preparations are used. When stored preparations are used (e.g., for 3 weeks at 40C), smaller-sized bands predominate (including bands at 32 and 27 kDa) resembling those in ref. 23, which indicate proteolytic activity. Antiserum prepared against the major 37-kDa protein species (anti-p37) was used to detect related coat protein species by immunoblotting (Fig. 1, lane 2). Major bands at 37 and 44 kDa (p37 and p44, respectively) as well as minor bands at 40, 57, 80, 90, and 96 kDa (p40, p57, p80, p90, and p96, respectively) were detected on the immunoblots, suggesting that these protein species may indeed share common sequences. Most likely p37 and p44 (and perhaps p40) are derived from p57 by proteolytic cleavage, and p80 and p96 are dimers of p37 and of p44, respectively (21,24 1824The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.