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We epigenotyped 211 individuals from 17 Zingiber kawagoii populations using methylation-sensitive amplification polymorphism (MSAP) and investigated the associations of methylated (mMSAP) and unmethylated (uMSAP) loci with 16 environmental variables. Data regarding genetic variation based on amplified fragment length polymorphism (AFLP) were obtained from an earlier study. We found a significant positive correlation between genetic and epigenetic variation. Significantly higher mean mMSAP and uMSAP uHE (unbiased expected heterozygosity: 0.223 and 0.131, respectively, p < 0.001) per locus than that estimated based on AFLP (uHE = 0.104) were found. Genome scans detected 10 mMSAP and 9 uMSAP FST outliers associated with various environmental variables. A significant linear fit for 11 and 12 environmental variables with outlier mMSAP and uMSAP ordination, respectively, generated using full model redundancy analysis (RDA) was found. When conditioned on geography, partial RDA revealed that five and six environmental variables, respectively, were the most important variables influencing outlier mMSAP and uMSAP variation. We found higher genetic (average FST = 0.298) than epigenetic (mMSAP and uMSAP average FST = 0.044 and 0.106, respectively) differentiation and higher genetic isolation-by-distance (IBD) than epigenetic IBD. Strong epigenetic isolation-by-environment (IBE) was found, particularly based on the outlier data, controlling either for geography (mMSAP and uMSAP βE = 0.128 and 0.132, respectively, p = 0.001) or for genetic structure (mMSAP and uMSAP βE = 0.105 and 0.136, respectively, p = 0.001). Our results suggest that epigenetic variants can be substrates for natural selection linked to environmental variables and complement genetic changes in the adaptive evolution of Z. kawagoii populations.

Ecological and evolutionary processes linking adaptation to environment are related to species’ range shifts. In this study, we employed amplified-fragment-length-polymorphism-based genome scan methods to identify candidate loci among Zingiber kawagoii populations inhabiting varying environments distributed at low to middle elevations (143–1488 m) in a narrow latitudinal range (between 21.90 and 25.30° N). Here, we show evidence of selection driving the divergence of Z. kawagoii. Twenty-six FST outliers were detected, which were significantly correlated with various environmental variables. The allele frequencies of nine FST outliers were either positively or negatively correlated with the population mean FST. Using several independent approaches, we found environmental variables act in a combinatorial fashion, best explaining outlier genetic variation. Nonetheless, we found that adaptive divergence was affected mostly by annual temperature range, and it is significantly positively correlated with latitude and significantly negatively correlated with the population mean FST. This study addresses a latitudinal pattern of changes in annual temperature range (which ranged from 13.8 °C in the Lanyu population to 18.5 °C in the Wulai population) and emphasizes the pattern of latitudinal population divergence closely linked to the allele frequencies of adaptive loci, acting in a narrow latitudinal range. Our results also indicate environmentally dependent local adaptation for both leading- and trailing-edge populations.

The testing association of environmental variables with genetic and epigenetic variation could be crucial to deciphering the effects of environmental factors playing roles as selective drivers in ecological speciation. Although ecological speciation may occur in closely related species, species boundaries may not be established over a short evolutionary timescale. Here, we investigated the genetic and epigenetic variations using amplified fragment length polymorphism (AFLP) and methylation-sensitive amplification polymorphism (MSAP), respectively, and tested their associations with environmental variables in populations of four closely related species in the R. pseudochrysanthum complex. No distinctive species relationships were found using genetic clustering analyses, neighbor-joining tree, and neighbor-net tree based on the total AFLP variation, which is suggestive of the incomplete lineage sorting of ancestral variation. Nonetheless, strong isolation-by-environment and adaptive divergence were revealed, despite the significant isolation-by-distance. Annual mean temperature, elevation, normalized difference vegetation index, and annual total potential evapotranspiration were found to be the most important environmental variables explaining outlier genetic and epigenetic variations. Our results suggest that the four closely related species of the R. pseudochrysanthum complex share the polymorphism of their ancestor, but reproductive isolation due to ecological speciation can occur if local environmental divergence persists over time.

ORA47 (octadecanoid-responsive AP2/ERF-domain transcription factor 47) of Arabidopsis thaliana is an AP2/ERF domain transcription factor that regulates jasmonate (JA) biosynthesis and is induced by methyl JA treatment. The regulatory mechanism of ORA47 remains unclear. ORA47 is shown to bind to the cis-element (NC/GT)CGNCCA, which is referred to as the O-box, in the promoter of ABI2. We proposed that ORA47 acts as a connection between ABA INSENSITIVE1 (ABI1) and ABI2 and mediates an ABI1-ORA47-ABI2 positive feedback loop. PORA47:ORA47-GFP transgenic plants were used in a chromatin immunoprecipitation (ChIP) assay to show that ORA47 participates in the biosynthesis and/or signaling pathways of nine phytohormones. Specifically, many abscisic acid (ABA) and JA biosynthesis and signaling genes were direct targets of ORA47 under stress conditions. The JA content of the P35S:ORA47-GR lines was highly induced under wounding and moderately induced under water stress relative to that of the wild-type plants. The wounding treatment moderately increased ABA accumulation in the transgenic lines, whereas the water stress treatment repressed the ABA content. ORA47 is proposed to play a role in the biosynthesis of JA and ABA and in regulating the biosynthesis and/or signaling of a suite of phytohormone genes when plants are subjected to wounding and water stress.

The question of what determines divergence both between and within species has been the central topic in evolutionary biology. Neutral drift and environmentally dependent divergence are predicted to play roles in driving population and lineage divergence. However, neutral drift may preclude adaptation if the rate of gene flow between populations is high. Here, we sampled populations of three Taiwania (Taiwania cryptomerioides) lineages occurring in Taiwan, the mainland of China (Yunnan-Myanmar border), and northern Vietnam, and tested the relative strength of neutral drift and divergent selection in shaping divergence of those populations and lineages. We quantified genetic and epigenetic variation, respectively, using amplified fragment length polymorphism (AFLP) and methylation-sensitive amplification polymorphism (MSAP). Analysis of 1413 AFLP and 462 MSAP loci using frequency-based genome scan methods and generalized linear models (GLMs) found no potential selective outliers when only Taiwanese populations were examined, suggesting that neutral drift was the predominant evolutionary process driving differentiation between those populations. However, environmentally associated divergence was found when lineages were compared. Thirty-two potential selective outliers were identified based on genome scans and their associations with environmental variables were tested with GLMs, generalized linear mixed effect models (GLMMs), and model selection with a model averaging approach. Ten loci (six AFLP and four MSAP) were found to be strongly associated with environmental variables, particularly monthly temperature variation and normalized difference vegetation index (NDVI) using model selection and a model averaging approach. Because only a small portion of genetic and epigenetic loci were found to be potential selective outliers, neutral evolutionary process might also have played crucial roles in driving lineage divergence, particularly between geographically and genetically isolated island and mainland Asia lineages. Nevertheless, the vast amount of neutral drift causing genetic and epigenetic variations might have the potential for adaptation to future climate changes. These could be important for the survival of Taiwania in different geographic areas.

Double digest restriction site-associated DNA sequencing (ddRADseq) is a tool for delivering genome-wide single nucleotide polymorphism (SNP) markers for non-model organisms useful in resolving fine-scale population structure and detecting signatures of selection. This study performs population genetic analysis, based on ddRADseq data, of a coniferous species, Keteleeria davidiana var. formosana, disjunctly distributed in northern and southern Taiwan, for investigation of population adaptive divergence in response to environmental heterogeneity. A total of 13,914 SNPs were detected and used to assess genetic diversity, FST outlier detection, population genetic structure, and individual assignments of five populations (62 individuals) of K. davidiana var. formosana. Principal component analysis (PCA), individual assignments, and the neighbor-joining tree were successful in differentiating individuals between northern and southern populations of K. davidiana var. formosana, but apparent gene flow between the southern DW30 population and northern populations was also revealed. Fifteen of 23 highly differentiated SNPs identified were found to be strongly associated with environmental variables, suggesting isolation-by-environment (IBE). However, multiple matrix regression with randomization analysis revealed strong IBE as well as significant isolation-by-distance. Environmental impacts on divergence were found between populations of the North and South regions and also between the two southern neighboring populations. BLASTN annotation of the sequences flanking outlier SNPs gave significant hits for three of 23 markers that might have biological relevance to mitochondrial homeostasis involved in the survival of locally adapted lineages. Species delimitation between K. davidiana var. formosana and its ancestor, K. davidiana, was also examined (72 individuals). This study has produced highly informative population genomic data for the understanding of population attributes, such as diversity, connectivity, and adaptive divergence associated with large- and small-scale environmental heterogeneity in K. davidiana var. formosana.

Double digest restriction site-associated DNA sequencing (ddRADseq) is a tool for delivering genome-wide single nucleotide polymorphism (SNP) markers for non-model organisms useful in resolving fine-scale population structure and detecting signatures of selection. This study performs population genetic analysis, based on ddRADseq data, of a coniferous species, Keteleeria davidiana var. formosana, disjunctly distributed in northern and southern Taiwan, for investigation of population adaptive divergence in response to environmental heterogeneity. A total of 13,914 SNPs were detected and used to assess genetic diversity, FST outlier detection, population genetic structure, and individual assignments of five populations (62 individuals) of K. davidiana var. formosana. Principal component analysis (PCA), individual assignments, and the neighbor-joining tree were successful in differentiating individuals between northern and southern populations of K. davidiana var. formosana, but apparent gene flow between the southern DW30 population and northern populations was also revealed. Fifteen of 23 highly differentiated SNPs identified were found to be strongly associated with environmental variables, suggesting isolation-by-environment (IBE). However, multiple matrix regression with randomization analysis revealed strong IBE as well as significant isolation-by-distance. Environmental impacts on divergence were found between populations of the North and South regions and also between the two southern neighboring populations. BLASTN annotation of the sequences flanking outlier SNPs gave significant hits for three of 23 markers that might have biological relevance to mitochondrial homeostasis involved in the survival of locally adapted lineages. Species delimitation between K. davidiana var. formosana and its ancestor, K. davidiana, was also examined (72 individuals). This study has produced highly informative population genomic data for the understanding of population attributes, such as diversity, connectivity, and adaptive divergence associated with large- and small-scale environmental heterogeneity in K. davidiana var. formosana.

Nucleotide-binding site-leucine-rich repeats (NBS-LRR) gene families are one of the major plant resistance genes. Genomic NBS evolution was studied in many plant species for diverse arrays of NBS gene families. In this study, we focused on one family of NBS sequences in an attempt to understand how closely related NBS sequences evolved in the light of selection in domesticated plant species. A phylogenetic analysis revealed five major clades (A–E) and five subclades (A1–A5) within clade A of cloned NBS sequences. Positive selection was only detected in newly evolved NBS lineages in subclades of clade A. Positively selected codon sites were found among NBS sequences of clade A. A sliding-window analysis revealed that regions with Ka/Ks ratios of >1 were in the inter-motifs when paired clades were compared, but regions with Ka/Ks ratios of >1 were found across NBS sequences when subclades of clade A were compared. Our results based on a family of closely related NBS sequences showed that positive selection was first exerted on specific lineages across all NBS sequences after selective constraints. Subsequently, sequences with mutations in commonly conserved motifs were scrutinized by purifying selection. In the long term, conserved high frequency alleles in commonly conserved motifs and changes in inter-motifs were maintained in the investigated family of NBS sequences. Moreover, codons identified to be under positive selection in the inter-motifs were mainly located in regions involved in functions of ATP binding or hydrolysis.

† Background and Aims Evolutionary and ecological roles of the chloroplast small heat shock protein (CPsHSP) have been emphasized based on variations in protein contents; however, DNA sequence variations related to the evolutionary and ecological roles of this gene have not been investigated. In the present study, a basal angiosperm, Machilus, together with the eudicot Rhododendron were used to illustrate the evolutionary dynamics of gene divergence in CPsHSPs. † Methods Degenerate primers were used to amplify CPsHSP-related sequences from 16 Rhododendron and eight Machilus species that occur in Taiwan. Manual DNA sequence alignment was carried out according to the deduced amino acid sequence alignment performed by CLUSTAL X. A neighbour-joining tree was generated in MEGA using conceptual translated amino acid sequences from consensus sequences of cloned CPsHSP genes from eight Machilus and 16 Rhododendron species as well as amino acid sequences of CPsHSPs from five monocots and seven other eudicots acquired from GenBank. CPsHSP amino acid sequences of Funaria hygrometrica were used as the outgroups. The aligned DNA and amino acid sequences were used to estimate several parameters of sequence divergence using the MEGA program. Separate Bayesian inference of DNA sequences of Rhododendron and Machilus species was analysed and the resulting gene trees were used for detection of putative positively selected amino acid sites by the Codeml program implemented in the PAML package. Mean hydrophobicity profile analysis was performed with representative amino acid sequences for both Rhododendron and Machilus species by the Bioedit program. The computer program SplitTester was used to examine whether CPsHSPs of Rhododendron lineages and duplicate copies of the Machilus CPsHSPs have evolved functional divergence based on the hydrophobicity distance matrix. † Key Results Only one copy of the CPsHSP was found in Rhododendron. However, a higher evolutionary rate of amino acid substitutions in the Hymenanthes lineage of Rhododendron was inferred. Two positively selected amino acid sites may have resulted in higher hydrophobicity in the region of the a-crystallin domain (ACD) of the CPsHSP. By contrast, the basal angiosperm, Machilus, possessed duplicate copies of the CPsHSP, which also differed in their evolutionary rates of amino acid substitutions. However, no apparent relationship of ecological relevance toward the positively selected amino acid sites was found in Machilus. † Conclusions Divergent evolution was found for both Rhododendron lineages and the paralogues of CPsHSP in Machilus that were directed to the shift in hydrophobicity in the ACD and/or methionine-rich region, which might have played important roles in molecular chaperone activity.

Quercus glauca (Thunb. ex Murray) Oerst (Fagaceae) has a wide distributional range in Taiwan. In this study, the evolutionary history and the most genetically divergent sites of Q. glauca were studied using a nuclear gene marker, glyceraldehyde‐3‐phosphate dehydrogenase. Also, the consistency of the results obtained from nuclear gene and cytoplasmic loci was investigated. Using a genealogical approach (TCS software), we determined haplotypes and their relationships to one another. We used the level of divergence for each population from the remaining populations (calculated as mean values of pairwise population differentiation, FST, for each population) to locate the most genetically divergent areas in Taiwan. According to the average FST of each population in comparison with the remaining ones, a peak was found in the northern part of central Taiwan, and another was found in the southeastern region. The peak profiles of the mean FST values for all three DNA data sets (nDNA, cpDNA, and mtDNA) showed simil...

Background and Aims The genetic variation and divergence estimated by allozyme analysis were used to reveal the evolutionary history of Castanopsis carlesii in Taiwan. Two major questions were discussed concerning evolutionary issues: where are the diversity centres, and where are the most genetically divergent sites in Taiwan? Methods Twenty-two populations of C. carlesii were sampled throughout Taiwan. Starch gel electrophoresis was used to assay allozyme variation. Genetic parameters and mean FST values of each population were analysed using the BIOSYS-2 program. Mean FST values of each population against the remaining populations, considered as genetic divergence, were estimated using the FSTAT program. Key Results Average values of genetic parameters describing the within-population variation, the average number of alleles per locus (A = 25), the effective number of alleles per locus (Ae = 138), the allelic richness (Ar = 238), the percentage of polymorphic loci (P = 69%), and the expected heterozygosity (He = 0270) were estimated. High levels of genetic diversity were found for C. carlesii compared with other local plant species. Genetic differentiation between populations was generally low. Conclusions From the data of expected heterozygosity, one major diversity centre was situated in central Taiwan corroborating previous reports for other plant species. According to the mean FST value of each population, the most divergent populations were situated in two places. One includes populations located in north central Taiwan between 2480N and 2420N. The other is located in south-eastern Taiwan between 2240N and 2310N. These two regions are approximately convergent with the most divergent locations determined for several other plant species using chloroplast DNA markers published previously. An important finding obtained from this study is that unordered markers like allozymes can be used to infer past population histories as well as chloroplast DNA markers do.

The genus Chamaecyparis comprises five species and one variety native to Taiwan, Japan, Canada, and USA, which demonstrates a classical eastern Asian, western North American, and eastern North American disjunct distributional pattern. The phylogenetic relationships of the species of Chamaecyparis were inferred by comparing 1130 bp of the combined data set of chloroplast trnV intron and petG-trnP intergenic spacer. The phylogenetic tree shows that Chamaecyparis nootkatensis (Cupressus nootkatensis or Xanthocyparis nootkatensis) is clearly diverged from other Chamaecyparis species. For Chamaecyparis species, C. thyoides is sister to C. formosensis and C. pisifera and these together form a monophyletic group. C. lawsoniana is sister to C. obtusa and C. taiwanensis; and these form another monophyletic group. Homogeneity in evolutionary rates was found among species in these two monophyletic groups. Results indicate the divergent evolution of C. taiwanensis and C. formosensis and molecular evidence in this investigation supports C. taiwanensis as a variety of C. obtusa. Utility of cpDNA intergenic spacer petG-trnP in Chamaecyparis is also discussed. Several biogeographical implications were inferred: (1) at least two divergence events have produced the eastern Asian, and both western and eastern North American disjunct distribution in Chamaecyparis; (2) intercontinental sister species pairs are found in Chamaecyparis; (3) cpDNA divergence between two intercontinental sister pairs of C. thyoides and C. pisifera, and C. lawsoniana and C. obtusa is 2.8% and 1.1%, which suggest an estimated divergence time of 14 and 5.5 million years ago during middle and late Miocene, respectively; (4) cpDNA divergence of two Asian Chamaecyparis groups between C. obtusa and C. taiwanensis, and between C. pisifera and C. formosensis is 0.25% and 0.57%, which suggest an estimated divergence time of 1.3 and 2.9 million years ago during Pleistocene and late Pliocene, respectively; these estimated divergence times suggest a relatively recent migration of Chamaecyparis to Taiwan from the Japanese Archipelago; (5) that climatic deterioration caused the disappearance of Chamaecyparis in continental Asia is probable.

We investigated the changes in antioxidative enzyme activities of two sweet potato cultivars under waterlogging and high-light conditions in the growth chamber. The activities of antioxidative enzymes were measured from leaf crude extract of sweet potato during the first five days of the treatments. Activities of superoxide dismutase and catalase were consistently increased in Taoyuan 1 sweet potato over time under waterlogging and high-light conditions. However, decreases in both superoxide dismutase and catalase activities were observed for cultivar Yongtsai under waterlogging and high-light conditions. Waterlogging, together with high-light intensity, impairs superoxide dismutase and catalase activities in the cultivar Yongtsai indicating its greater susceptibility to waterlogging and high-light stress. In contrast, the increase in activities of superoxide dismutase and catalase in Taoyuan 1 indicated its greater ability to detoxify reactive oxygen species during the treatment and ensured its reduced susceptibility to waterlogging and high-light stress. The activities of peroxidase may be inactivated by high-light treatment and, therefore, may not be associated with tolerance of sweet potato plants to waterlogging and high-light stress. Differences in susceptibility to waterlogging and high-light conditions in the leafy vegetable Yongtsai and storage root Taoyuan 1 are discussed.

Based on fossil pollen, the distribution range of Taiwan fir [Abies kawakamii (Hay.) Ito] (Pinaceae) is smaller than it was 50 000 years ago. To characterize the present refuge populations of A. kawakamii, which survive only in subalpine forests in Taiwan, we surveyed nuclear genes and chloroplast intergenic spacers to assess the genetic diversity of Taiwan fir. Populations maintain high genetic diversity and contain similar numbers of haplotypes for the GapC (cytosolic glyceraldehyde 3-phosphate dehydrogenase) fragment. Haplotypes for GapC are generally widespread, and population-specific haplotypes accounted for 2.5% of the total. Differentiation among populations is very low (G(ST) = 0.01). Only three haplotypes were detected for the cpDNA marker, and every population had one or two haplotypes. In a neutrality test, the variation in nucleotides did not deviate from that expected with neutral evolution for either marker. A retreat route to higher elevations was not evident from either the GapC or cpDNA markers. Hsuehshan was the site of the most divergent population in Taiwan. We concluded that uniform genetic diversity, low differentiation, low numbers of population-specific haplotypes, and neutral evolution characterize contemporary refuge populations of Taiwan fir.

†Background and Aims Positive selection in the a-crystallin domain (ACD) of the chloroplast small heat shock protein (CPsHSP) gene was found in a previous study and was suggested to be related to the ecological adaptation of Rhododendron species in the subgenus Hymenanthes. Consequently, it was of interest to examine whether gene duplication and subsequent divergence have occurred in other sHSP genes, for example class I cytosolic sHSP genes (CT1sHSPs )i nRhododendron in Taiwan, where many endemic species have evolved as a result of habitat differentiation. †Methods A phylogeny of CT1sHSP amino acid sequences was built from Rhododendron, Arabidopsis thaliana, Oryza sativa, Populus trichocarpa, Vitis vinifera and other species for elucidation of the phylogenetic relationships among CT1sHSPs. Phylogenies of Rhododendron CT1sHSP nucleotide and amino acid sequences were generated for positive selection and functional divergence analysis, respectively. Positively selected sites and amino acid differences between types of Rhododendron CT1sHSPs were mapped onto the wheat sHSP16.9 protein structure. Average genetic distance (Dxy) and dN/dS ratios between types of Rhododendron CT1sHSP genes were analysed using sliding window analysis. Gene conversion was also assessed between types of Rhododendron CT1sHSPs. †Key Results Two types of Rhododendron CT1sHSP were identified. A high level of genetic similarity and diversity within and flanking the ACD, respectively, between types of Rhododendron CT1sHSP were found. Main differences between the two types of Rhododendron CT1sHSPs were: (1) increased hydrophobicity by two positively selected amino acid sites and a seven-amino-acid insertion in the N-terminal arm; and (2) increased structural flexibility and solubility by a seven-amino-acid insertion in the N-terminal arm and one positively selected amino acid site in the C-terminal extension. †Conclusions Functional conservation of the ACD of Rhododendron CT1sHSP genes was inferred because of strong purifying selection. However, sequence variations flanking the ACD inRhododendronCT1sHSP gene duplicates may have resulted in functional divergence and played important roles in chaperon function enhancement.

The difference among florets within a panicle in grain filling and four hormone contents was compared by using two rice varieties differing in panicle type, i.e. compact-panicle variety Xiushui 994 and loose-panicle variety Xiushui 11. Meanwhile the effect of changing source (leaf cutting) and sink (floret removal) on grain filling and four hormone (indole-3-acetic acid, gibberellin, zeatin riboside and abscisic acid)level dynamics in developing grains was also examined. The results showed that Xiushui 994 had greater variation in grain filling rate (GFR), grain weight, filled grain percent (FGP) and four hormone contents during grain filling than Xiushui 11. Moreover, the former variety also showed the greater difference in the time of having the highest hormone contents between superior and inferior florets. The change in source and sink size had great effect on grain filling process and dynamics of four hormone contents, and the extent of the effect varied with variety and floret type. For Xiushui 994, floret-removal treatment had little effect on grain weight and FGP of the superior florets, but caused a marked decrease in GFR and four hormone contents, and a delay in the time when the highest GFR and hormone contents occurred. In the source-reducing treatment, GFR, grain weight and FGP for both superior and interior florets were all decreased. For Xiushui 11, both treatments had little effect on grain development in terms of grain filling properties and hormone content change in the two types of florets. The results indicated that the grain filling of compact-panicle variety is more source-limited than that of loose-panicle one, and relative level of hormone in both superior and inferior florets determined development of inferior florets.

Demographic history and dispersal ability are significant factors in determining the genetic composition of a population. In this study, we examined the phylogeographic patterns of Ceriops tagal from the Hainan Island and the Gulf of Thailand in the South China Sea, where there are abundant mangrove species. Nucleotide variations in two chloroplast DNA spacers were compared with trace Ceriops propagule dispersal routes and demographic history. An analysis of Templeton, Crandall and Sing’s (TCS) parsimonious networks and population demographics suggests that the Ceriops population gradually expanded from the northern parts of the South China Sea to the south-western populations in the Gulf of Thailand. Such phylogeographic inferences reflect a postglacial southward shift in the mangrove genetic diversity centre and a connection between the demographic dynamics and the coastal range expansion caused by the sea-level rise in the Pleistocene. Therefore, the phylogeographic pattern and historical demography of mangrove species were affected by glaciations during the Pleistocene such as temperate biota.

Flooding is a frequently occurring environmental stress that can severely affect plant growth. This study shows that treatment of corn (Zea mays L.) seedlings with abscisic acid (ABA) increases their tolerance to anoxia 10-fold over untreated seedlings and twofold over seedlings treated with water. Corn seedlings stressed anoxically for 1 day showed only 8% survival when planted in vermiculite. Pretreatment of root tips with 100 micromolar ABA or water for 24 hours before the 1 day anoxic stress increased the anoxic survivability of seedlings to 87% and 47%, respectively. Cycloheximide (5 milligrams per liter), added together with ABA, reduced the seedling survival rate, indicating that the induction of anoxic tolerance in corn by ABA was partly a result of the synthesis of new proteins. ABA treatment induced a threefold increase in alcohol dehydrogenase enzyme activity in corn roots. However, after 24 h of anoxia, alcohol dehydrogenase enzyme activity between the ABA-pretreated and non-pretreated corn roots was not significantly different. The results indicated that ABA played an important role in inducing anoxic tolerance in corn and that the induced tolerance was probably mediated by an increase in alcohol dehydrogenase enzyme activity before the anoxic stress.

Background CBF/DREB duplicate genes are widely distributed in higher plants and encode transcriptional factors, or CBFs, which bind a DNA regulatory element and impart responsiveness to low temperatures and dehydration. Results We explored patterns of genetic variations of CBF1, -2, and -3 from 34 accessions of Arabidopsis thaliana. Molecular population genetic analyses of these genes indicated that CBF2 has much reduced nucleotide diversity in the transcriptional unit and promoter, suggesting that CBF2 has been subjected to a recent adaptive sweep, which agrees with reports of a regulatory protein of CBF2. Investigating the ratios of Ka/Ks between all paired CBF paralogus genes, high conservation of the AP2 domain was observed, and the major divergence of proteins was the result of relaxation in two regions within the transcriptional activation domain which was under positive selection after CBF duplication. With respect to the level of CBF gene expression, several mutated nucleotides in the promoters of CBF3 and -1 of specific ecotypes might be responsible for its consistently low expression. Conclusion We concluded from our data that important evolutionary changes in CBF1, -2, and -3 may have primarily occurred at the level of gene regulation as well as in protein function.

An allelopathic interaction of a pasture-forest intercropping system was evaluated by experiments conducted in field and by laboratory assays. A study site was situated in the farm of Hoshe Forestry Experiment Station at Nantou County, Taiwan. After deforestation of Chinese fir (Cunninghamia lanceolata), a split plot design of 4 treatments, namely litter removed, litter removed and kikuyu grass (Pennisetum clandestinum) planted, litter left, and litter left and grass planted, was composed. Field meaurements showed that the fir litter left on the ground did not significantly inhibit the growth of weeds, kikuyu grass, and fir seedlings in the first four months following deforestation, while kikuyu grass significantly suppressed the growth of weeds longer than four months but did not reduce growth of fir seedlings. The aqueous extracts of fresh fir leaves, fir litter, and kikuyu leaves were bioassayed by using lettuce and rice seeds and stolon cuttings ofBrachiaria mutica. Bioassays showed that fresh fir leaves produced significant phytotoxicity while fir litter and kikuyu grass gave limited toxicity. Nine phytotoxic phenolics and many unidentified flavonoids were found in the leaf and litter of Chinese fir and kikuyu leaves. A good correlation between the degree of phytotoxicity and phytotoxins was obtained, indicating an allelopathy was involved. This finding suggests that allelopathy may contribute benefits in the intercropping system to reduce the need for herbicides and to lessen the labor cost for weed control.