;The transcription factors DREB1s/CBFs specifically interact with the DRE/CRT cis-acting element (core motif: G/ACCGAC) and control the expression of many stressinducible genes in Arabidopsis. We isolated a cDNA for a DREB1/CBF homolog, ZmDREB1A in maize using a yeast one-hybrid system. The ZmDREB1A proteins specifically bound to DRE and the highly conserved valine at the 14th residue in the ERF/AP2 DNA binding domain was a key to determining the specific interaction between this protein and the DRE sequence. Expression of ZmDREB1A was induced by cold stress and slightly increased by highsalinity stress. This gene was also transiently expressed by mechanical attack. ZmDREB1A activated the transcription of the GUS reporter gene driven by DRE in rice protoplasts. Overexpression of ZmDREB1A in transgenic Arabidopsis induced overexpression of target stress-inducible genes of Arabidopsis DREB1A resulting in plants with higher tolerance to drought and freezing stresses. This indicated that ZmDREB1A has functional similarity to DREB1s/CBFs in Arabidopsis. The structure of the ERF/ AP2 domain of ZmDREB1A in maize is closely related to DREB1-type ERF/AP2 domains in the monocots as compared with that in the dicots. ZmDREB1A is suggested to be potentially useful for producing transgenic plants that is tolerant to drought, high-salinity and/or cold stresses.

Summary1. Increasingly, ecologists are using functional and phylogenetic approaches to quantify the relative importance of stochastic, abiotic filtering and biotic filtering processes shaping the pattern of species co-occurrence. A remaining challenge in functional and phylogenetic analyses of tropical tree communities is to successfully integrate the functional and phylogenetic structure of tree communities across spatial and size scales and habitats in a single analysis. 2. We analysed the functional and phylogenetic structure of tree assemblages in a 20-ha tropical forest dynamics plot in south-west China. Because the influence of biotic interactions may become more apparent as cohorts age, on local scales, and in resource-rich environments, we perform our analyses across three size classes, six spatial scales and six distinct habitat types, using 10 plant functional traits and a molecular phylogeny for the >400 tree taxa found in the plot. 3. All traits, except leaf area and stem-specific resistance, had significant, albeit weak phylogenetic signal. For canopy species, phylogenetic clustering in small and medium size classes turned to phylogenetic overdispersion in the largest size class and this change in dispersion with size was found in each habitat type and across all spatial scales. On fine spatial scales, functional dispersion changed from clustering to overdispersion with increasing size classes. However, on larger spatial scales assemblages were functionally clustered for all size classes and habitats. 4. Phylogenetic and functional structure across spatial and size scales and habitats gave strong support for a deterministic model of species co-occurrence rather than for a neutral model. The results also support the hypothesis that abiotic determinism is more important at larger scales, while biotic determinism is more important on smaller scales within habitats.

Persea can be retained as a genus by the inclusion of Apollonias barbujana and exclusion a few species that do not fit into the established subgenera. A major revision is recommended for the delimitation between Alseodaphne, Dehaasia, and Nothaphoebe. We suggest that the Persea group originated from the Perseeae-Laureae radiation in early Eocene Laurasia. Its amphi-pacific disjunction results from the disruption of boreotropical flora by climatic cooling during the mid- to late Eocene. The American-Macaronesian disjunction may be explained by the long-distance dispersal.

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