Search

Flowering cherry is an extremely renowned ornamental tree, consisting of a variety of species and cultivars. Because cherry species have no strict barriers for interspecific hybridization before fertilization, identification of the gene underlying post-zygotic hybrid inviability will help breeders identify specimens for breeding and help us understand speciation mechanisms. In this study, we mapped the genetic linkages and physical genome sequences for a presumed hybrid inviability locus (HIs-1) that we observed in the seedlings crossed between Cerasus × yedoensis 'Somei-yoshino' and its wild relative C. spachiana. By the surveying linkage maps of 'Somei-yoshino' and C. spachiana, we identified correlation with seedling inviability only in linkage group 4 (LG4) of the 'Somei-yoshino' map. When we produced a finer-scaled map of HIs-1 in LG4, we found that HIs-1 is located between two microsatellite (SSR) markers with a 3.8 cM span. Using eight SSR markers based on peach genome sequences, we further refined the candidate region for HIs-1. This region was located between Pp04C001 and Pp04C007 markers, spanning 240 Kb of the peach genome, in which 45 transcribed genes had been estimated. From these candidate genes, it will be feasible to identify molecular mechanisms involved in cherry hybrid inviability.

Many wild populations of Chamaecyparis pisifera (Cupressaceae) are recently fragmented and surrounded by coniferous plantations. To distinguish the species composition of pollens that are dispersed to female flowers of C. pisifera, genetic markers (Chaps-trnL01 and Chaps-trnL02) were developed based on the differences in trnL (UAA) intron region of chloroplast DNA. This region in C. pisifera contains the site of the Cla I restriction enzyme and allows the distinction of C. pisifera from other Cupressaceae species after digestion of the products with the enzyme resulting in the development of cleaved amplified polymorphic sequence (CAPS) markers. The availability of markers was determined by single-pollen genotyping. Amplification success rates of 75.0, 58.3, and 100% were obtained for the pollens of C. pisifera, Chamaecyparis obtusa, and Cryptomeria japonica, respectively. Then, the markers and genotyping methods were applied to airborne pollen grains sampled from a remnant natural stand of C. pisifera. Over 90% of the pollen grains were identified as belonging to C. obtusa. Thus, we concluded that abundant heterospecific pollen dispersal was present during the flowering periods of C. pisifera. These results suggest that the remnant C. pisifera population might suffer reproductive interference due to the lower chances to be pollinated with conspecific pollens.

Japanese flowering cherry (Prunus subgenus Cerasus) cultivars, which are characterized by beautiful flowers, have been developed through hybridization among wild Prunus taxa. The long history of cultivation has caused significant confusion over the origins of these cultivars. We conducted molecular analysis using nuclear simple sequence repeat (SSR) polymorphisms to trace cultivar origins. Bayesian clustering based on the STRUCTURE analysis using SSR genotypes revealed that many cultivars originated from hybridization between two or more wild species. This suggests that morphological variations among flowering cherry cultivars probably arose through a complex sequence of hybridizations. Our findings generally supported estimates of the origins of cultivars based on morphological study, although there were some exceptions.

Pyrus calleryana var. dimorphophylla, a variety of Callery pear (Pyrus calleryana), is endemic to the Tokai district of central Japan, and is currently listed as “Endangered”. The remnant habitats and trees are of limited number, and highly fragmented. As the first step in determining appropriate conservation units, genetic diversity and differentiation in this species were investigated using chloroplast DNA (cpDNA) and nuclear simple sequence repeat (SSR) polymorphisms. All possible remnant trees were genotyped, then six populations were defined based on the results of cpDNA haplotype determination and Bayesian clustering approaches performed using the SSR locus data. Some trees appeared to originate from artificial propagation. Some individuals were difficult to differentiate genetically from the related species, Pyrus × uyematsuana, which is considered to be a hybrid between P. calleryana var. dimorphophylla and a possibly naturalized species, Pyrus pyrifolia, implying that introgression between these species may have occurred. In P. calleryana var. dimorphophylla, anthropogenic factors such as propagation and related species planting are probably major causes of complexity in the genetic structure.

Mating processes of local demes and spatial genetic structure of island populations at the self-incompatibility (S-) locus under negative frequency-dependent selection (NFDS) were evaluated in Prunus lannesiana var. speciosa in comparison with nuclear simple sequence repeat (SSR) loci that seemed to be evolutionarily neutral. Our observations of local mating patterns indicated that male-female pair fecundity was influenced by not only self-incompatibility, but also various factors, such as kinship, pollen production and flowering synchrony. In spite of the mating bias caused by these factors, the NFDS effect on changes in allele frequencies from potential mates to mating pollen was detected at the S-locus but not at the SSR loci, although the changes from adult to juvenile cohorts were not apparent at any loci. Genetic differentiation and isolation-by-distance over various spatial scales were smaller at the S-locus than at the SSR loci, as expected under the NFDS. Allele-sharing distributions among the populations also had a unimodal pattern at the S-locus, indicating the NFDS effect except for alleles unique to individual populations probably due to isolation among islands, although this pattern was not exhibited by the SSR loci. Our results suggest that the NFDS at the S-locus has an impact on both the mating patterns and the genetic structure in the P. lannesiana populations studied.

Timing of acorn development and abortion is an important maternal strategy in oak sexual reproduction. To understand the significance of acorn abortion in Quercus serrata, artificial pollination of different mating patterns (outcross, self-, and nonpollination) was performed, and the timing of abortion and the size and internal development of acorns from each mating type were investigated. Acorns were aborted similarly in every pollination treatment until 80 days after pollination. Almost all self- and nonpollinated acorns were rapidly aborted during the period 80–120 days after pollination. During that period, differences in internal fruit development between outcross-pollinated and unsuitably pollinated (self- and nonpolinated) acorns were observed. In addition, cotyledon development and a rapid increase in fruit size were observed in the acorns gained by outcross pollination. The correspondence between the timing of abortion and the timing of rapid size growth and the development of storage organs suggests that this acorn-maintenance strategy may be the consequence of a maternal adaptation that allows better reproductive success under resource limitation.

ソメイヨシノのような園芸品種の大規模植栽はサクラ野生種の遺伝子撹乱を引き起こす可能性がある。本研究ではソメイヨシノからサクラ野生種への遺伝子流動を調べるため, 自家不和合性 (S) 遺伝子の高い多型性に注目して, ソメイヨシノ由来のS対立遺伝子を検出する遺伝マーカーを開発した。サクラ野生種個体から採取した種子を分析したところ, サクラ野生種個体の中にソメイヨシノと同じS対立遺伝子をもつ個体が存在していたため, 開発した遺伝マーカーだけではそれらの個体とソメイヨシノに由来するS対立遺伝子を区別できなかった。しかしながら, SSR分析を組み合わせることでソメイヨシノ由来のS対立遺伝子を判別することは可能であり, 開発した遺伝マーカーとSSRマーカーを併用することはソメイヨシノ由来のゲノムの拡散パターンを調べる上で有効な手段であると考えられる。

Simple sequence repeat (SSR) markers were developed for the flowering cherry Cerasus jamasakura (also known as Prunus jamasakura) using 31,995 expressed sequence tags (ESTs) from the NCBI database. Out of 96 of designed primer pairs, 63 showed clear PCR amplification and 13 of these revealed polymorphism in eight individuals sampled across the species’ range. The number of alleles detected and expected heterozygosity ranged from 1 to 8 and 0.000 to 0.833, respectively, when these 13 loci were examined in 23 individuals from a single population. For all except one of the lcoi, polymorphism was also detected in at least four of six other taxa of flowering cherries examined. The results show that the developed EST-SSRs are highly transferable, and that these markers are likely to be useful in studies of the population genetics of flowering cherries.

Pollen-mediated gene flow was analyzed in a small, fragmented, natural population of Fagus crenata Blume by surveying five microsatellite markers in seedlings derived from open-pollinated crosses. Paternity of 162 seedlings derived from two maternal trees was assigned by the maximum-likelihood method using CERVUS 2.0, and pollen dispersal patterns within the study site were determined. Most of the trees within the site sired seeds, although we found evidence of limited pollen-mediated gene flow from outside the stand; 92% of the matings that generated the seedlings occurred between trees within the population, and 8% of the matings were mediated by pollen derived from trees located outside the study site. Although the pollen-mediated gene flow within the site was not strongly limited, mating frequencies of paternal trees were found to be weakly negatively correlated with their distance from the mother trees, positively correlated with their stem diameter at breast height, and uncorrelated with their relatedness to the mother trees.

Cerasus × yedoensis ‘Somei-yoshino’ (2n = 16), one of the most popular cultivars of Japanese flowering cherry, is considered a hybrid between Cerasus spachiana and Cerasus speciosa. In the present study, we observed segregation of the trait for seedling growth in F 1 progenies of Somei-yoshino. In all three families crossed with ancestral wild species, C. spachiana, approximately half of the seedlings showed growth failure. To identify loci involved in seedling inviability, we constructed a genetic linkage map of Somei-yoshino. Both normal growth (N = 77) and growth failure seedlings (N = 101) of an F 1 progenies crossed between Somei-yoshino (CY) and C. spachiana (E750) were used for map construction. In accordance to pseudo-testcross strategy, female (CY) and male (E750) linkage maps were constructed. The CY map consists of eight linkage groups with 59 simple sequence repeat (SSR) and 17 amplified fragment length polymorphism (AFLP) markers. The map length is 574.9 cM. In contrast, the E750 map reached 196.8 cM and included 17 SSRs. Subsequently, we explored positions of loci associated to seedling inviability along with linkage maps. Results of segregation distortion of markers, association analysis, and interval mapping consistently showed that an inviability gene was located between two SSR markers, EMPaS13 and BPPCT005 in the fourth linkage group (LG4) of the Somei-yoshino map with 99.6 % explanations for the inviability trait but not present in LG4 of the E750 map. From the genotypes and expressions of seedling inviability, we named the locus Hybrid Inviability of seedlings 1 (HIs1). Finally, HIs1 was mapped to LG4 as Mendelian trait loci and was completely linked with an SSR, EMPaS13. Although the mechanisms of seedling inviability cannot be explained by only one locus model of HIs1, one of the candidate genes involved in hybrid incompatibility between Somei-yoshino and C. spachiana is certainly located on LG4 of the CY map.

Background: Cry j 2 is one of the major pollen allergens of Cryptomeria japonica. The polymorphism of Cry j 2 isoforms and the conservation of the structure of Cry j 2 in coniferous species remain to be analyzed. Methods:A cDNA library derived from the pollen of C. japonica was screened using a fragment of Cry j 2 cDNA. Restriction fragment length polymorphism analysis was performed to examine the diversity of Cry j 2 genes. The promoters of Cry j 2 genes were isolated with a commercially available cloning kit. Clonal variations in the expression of Cry j 2 in pollen were examined by RNA gel blot analysis, and the conservation of the structure of the Cry j 2 gene in coniferous species was evaluated by DNA gel blot analysis. Results: We isolated three cDNA clones encoding novel isoforms of Cry j 2. We also sequenced a total of 16 promoter regions from 10 specimens. The sequences of promoter regions of Cry j 2 genes were highly divergent. The amount of Cry j 2 mRNA also varied considerably. The Cry j 2 gene was found to be conserved among species belonging to Taxodiaceae and Cupressaceae but to vary between Taxodiaceae and Pinaceae. Conclusions: The coding and promoter regions of Cry j 2 genes contain large numbers of polymorphisms. Our analysis revealed large variations in the expression of Cry j 2 at the transcriptional level, and we suggest that conserved homologs of Cry j 2 confer cross-allergenicity among Taxodiaceae and Cupressaceae.

The physiological response of leaves developed in low light (L) on Fagus crenata seedlings exposed to different levels of high light (H: high light, M: medium light) was studied. Measurements were conducted on potted seedlings in the F. crenata forest understory. The seedlings with leaves developed in L were transferred to H (L–H) and M (L–M) in summer. On exposure to high light, the photochemical efficiency of dark-adapted PSII ( F v / F m ) immediately decreased and was followed by a subsequent recovery in both L–H and L–M leaves. The mean value of F v / F m in L–H leaves was lower than that in L–M leaves through experiments, indicating that the degree of photoinhibition in L–H leaves was greater than that in L–M leaves. About 1 month after transfer, 37% and 5% of leaves had fallen in L–H and L–M seedlings, respectively. This result also indicated the greater photoinhibition in L–H leaves. Moreover, the photosynthetic capacity ( P N max ) of L–H leaves decreased. In contrast, the P N max of L–M leaves increased, although the P N max was lower than that of M control leaves. An increase in the xanthophyll cycle pool (VAZ), indicating an increase of the photoprotective function, was found in both L–H and L–M leaves. Especially, the VAZ pool in L–M leaves was higher than that in M leaves by the end of experiments. L–M leaves may avoid photoinhibition effectively by the decrease in excess light with the increase of the P N max or VAZ pool, compared to L–H leaves. Thus, the physiological acclimation on exposure to high light depended on the degree of high light. To achieve successful photosynthetic acclimation with slight photoinhibition, the variation of light intensity before and after exposure to high light would be an important factor because of the difference in excess light.

In the Rosaceae family, which includes Prunus, gametophytic self-incompatibility (GSI) is controlled by a single multiallelic locus (S-locus), and the S-locus product expressed in the pistils is a glycoprotein with ribonuclease activity (S-RNase). Two populations of flowering cherry (Prunus lannesiana var. speciosa), located on Hachijo Island in Japan's Izu Islands, were sampled, and S-allele diversity was surveyed based on the sequence polymorphism of S-RNase. A total of seven S-alleles were cloned and sequenced. The S-RNases of flowering cherry showed high homology to those of Prunus cultivars (P. avium and P. dulcis). In the phylogenetic tree, the S-RNases of flowering cherry and other Prunus cultivars formed a distinct group, but they did not form species-specific subgroups. The nucleotide substitution pattern in S-RNases of flowering cherry showed no excess of nonsynonymous substitutions relative to synonymous substitutions. However, the S-RNases of flowering cherry had a higher Ka/Ks ratio than those of other Prunus cultivars, and a subtle heterogeneity in the nucleotide substitution rates was observed among the Prunus species. The S-genotype of each individual was determined by Southern blotting of restriction enzyme-digested genomic DNA, using cDNA for S-RNase as a probe. A total of 22 S-alleles were identified. All individuals examined were heterozygous, as expected under GSI. The allele frequencies were, contrary to the expectation under GSI, significantly unequal. The two populations studied showed a high degree of overlap, with 18 shared alleles. However, the allele frequencies differed considerably between the two populations.

To examine the role of rhodoxanthin in long-term acclimation to low temperatures, we monitored seasonal changes in pigment composition, photosynthesis, chlorophyll fluorescence and the level of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in needles of wild-type and mutant forms of Cryptomeria japonica. In winter, rhodoxanthin accumulated in sun-exposed needles of wild-type plants, but not in those of the mutant. The level of chlorophyll decreased in both types of plant in winter. In contrast, the level of the xanthophyll cycle pool increased in both cases. The level of the pool in the mutant was twice that in the wild type in winter, on a Chl basis, even though the levels in both were similar in summer. The synthesis of rhodoxanthin might be triggered by photo-inhibitory conditions, as suggested by the sustained elevated levels of zeaxanthin (Z) and antheraxanthin (A). In the wild type and the mutant, the quantum yield of CO2 fixation (φ), the photosynthetic capacity, the photochemical efficiency of photosystem II (PSII), the photochemical quenching and the level of Rubisco in summer were similar. However, all these values for the wild type were higher than those for the mutant in winter. The non-photochemical quenching (NPQ) in the mutant in winter increased rapidly even under low light conditions due to the high sustained levels of Z and A. In contrast, in the wild type, the conversion of Z via A to rhodoxanthin prevented the rapid increase in NPQ to maintain the relatively high level of φ. These findings suggest that rhodoxanthin might play an important photoprotective role in long-term acclimation to cold. The dynamic regulation of the amount of rhodoxanthin relative to the level of the xanthophyll cycle pool might act to maintain an appropriate balance between light absorption, photosynthesis and the thermal dissipation of energy due to excess absorbed light in winter.

This study focused on the physiological changes inCryptomeria japonica accompanied by needle color changes during the winter. The physiological measurements include gas exchange, chlorophyll fluorescence, pigments, active oxygen scavenging enzymes, and several proteins in the photosynthetic apparatus. The light-saturated photosynthesis decreased during the winter. Total chlorophyll content and chlorophylla/b ratio decreased; meanwhile xanthophyll cycle pigments and lutein contents increased significantly. These results indicate that cold acclimation had occurred. Photoinhibition was also observed inC. japonica which can be determined from the decreases in photochemical efficiency of PS II and the partial closure of PS II reaction centers. Small and large subunits of Rubisco and LHC II in the needles ofC. japonica showed only a slight decrease during the winter, indicating that photoinhibition inC. japonica probably reflects a protective process to prevent more severe damage to the photosynthetic apparatus during low-temperature stress.

Genetically transformed Japanese white birch ( Betula platyphylla var. japonica ) plants were regenerated after co-cultivation of leaf discs with Agrobacterium tumefaciens strain LBA4404 that harbored a binary vector (pBI121) which included genes for β -glucuronidase (GUS) and neomycin phosphotransferase. The efficiency of Agrobacterium tumefaciens -mediated transformation of Japanese white birch was markedly increased by the inclusion of acetosyringone in the co-cultivation medium. Successful transformation was confirmed by the ability of leaf discs to produce calli in the presence of kanamycin, by histochemical and fluorometric assays of GUS activity in plant tissues, and by Southern blot analysis. With this transformation system, about 4 months were required for regeneration of the transgenic birch plants from leaf discs. The frequency of transformation was approximately 18%.

We evaluated seasonal variation in photosynthetic temperature dependence and its contribution to annual carbon gain in an evergreen understorey shrub, Daphniphyllum humile Maxim, growing at the forest border and in the understorey of a deciduous forest. Plants at both sites exhibited similar optimal temperatures for photosynthesis (T(opt)). The activation energy for ribulose-1,5-bisphosphate (RuBP) carboxylation (HaV) at both sites tended to be higher in summer than in spring or autumn, suggesting that HaV may be the controlling factor in the T(opt) shift in D. humile. In contrast to the seasonal changes in T(opt ), the maximum photosynthetic rate at the optimal temperature (P(opt)) differed between the two sites: it was lower in autumn than in summer at the forest border, but was the same in summer and autumn in the understorey. In the understorey plants, nitrogen content (Narea) increased in autumn, but this was not the case for forest border plants. In addition, Rubisco content increased significantly in autumn in the understorey leaves but decreased distinctly in forest border leaves. Increased Narea and Rubisco in understorey leaves resulted in increased in photosynthesis in autumn. Annual carbon gain was 30.8 mol · m(-2) in forest border leaves and 5.8 mol · m(-2) in understorey leaves. Carbon gain in understorey leaves during the short period after overstorey leaf fall and before snow accumulation was approximately 49% of annual carbon gain. Furthermore, autumn carbon gain calculated using activation energy of summer with autumn photosynthetic parameters underestimated the autumn carbon gain by as much as 31%. In conclusion, photosynthetic temperature acclimation may be a key factor in increasing annual carbon gain in understorey D. humile.

Precursors to small subunits (SSU) of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) and apoproteins of light-harvesting chlorophyll a/b binding protein (LHCPII) in photosystem II were synthesized in vitro by expressing pine (Pinus thunbergii Parl.) cDNA clones encoding these proteins. The precursors to pine SSU and LHCPII were post-translationally transported into spinach chloroplasts, processed into mature size, and localized in only stroma and thylakoid membranes, respectively. The pine SSU was tightly integrated into spinach Rubisco; however, the pine LHCPII was not found in the light-harvesting chlorophyll–protein complex. These results suggest that a common biogenesis pathway of nuclear-encoded chloroplast proteins is present both in gymnosperms and in angiosperms.

The wild flowering cherry Prunus lannesiana var. speciosa is highly geographically restricted, being confined to the Izu Islands and neighboring peninsulas in Japan. In an attempt to elucidate how populations of this species have established we investigated the genetic diversity and differentiation in seven populations (sampling 408 individuals in total), using three kinds of genetic markers: chloroplast DNA (cpDNA), amplified fragment length polymorphisms (AFLPs), and 11 nuclear SSR polymorphic loci. Eight haplotypes were identified based on the cpDNA sequence variations, 64 polymorphic fragments were scored for the AFLP markers, and a total of 154 alleles were detected at the 11 nuclear SSR loci. Analysis of molecular variance showed that among-population variation accounted for 16.55, 15.04 and 7.45% of the total detected variation at the cpDNA, AFLPs, and SSR loci, respectively. Thus, variation within populations accounted for most of the genetic variance for all types of markers, although the genetic differentiation among populations was also highly significant. For cpDNA variation, no clear structure was found among the populations, except that of the most distant island, although an "isolation by distance" pattern was found for each marker. Both neighbor-joining trees and structure analysis indicate that the genetic relationships between populations reflect geological variations between the peninsula and the islands and among the islands. Furthermore, hybridization with related species may have affected the genetic structure, and some genetic introgression is likely to have occurred.

In angiosperms, light has been shown to induce the expression of cab and rbcS genes, which encode the apoprotein of light-harvesting chlorophyll a/b binding protein (LHCP) and the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), respectively. By contrast, chlorophylls are synthesized in the cotyledons of pine seedlings even if seeds are germinated in the dark. We have examined the expression of cab and rbcS genes in the cotyledons of pine (Pinus thunbergii) seedlings grown in darkness. The proteins of LHCP and the large subunit and the small subunit of Rubisco were detected in the cotyledons of dark-grown seedlings. The transcripts of cab and rbcS genes were present at substantial levels in dark-grown seedlings. However, the transcripts and the translated products of the genes were not found in the embryos of dry seeds. These results indicate that light is not required for the expression of cab and rbcS genes during the course of development of the cotyledons of pine seedlings. The processing of the precursor polypeptides of the mature proteins also appears to take place even in the dark.

The genetic resources of a particular species of flowering cherry, Cerasus jamasakura, have high conservation priority because of its cultural, ecological and economic value in Japan. Therefore, the genetic structures of 12 natural populations of C. jamasakura were assessed using ten nuclear SSR loci. The population differentiation was relatively low (F (ST), 0.043), reflecting long-distance dispersal of seeds by animals and historical human activities. However, a neighbor-joining tree derived from the acquired data, spatial analysis of molecular variance and STRUCTURE analysis revealed that the populations could be divided into two groups: one located on Kyusyu Island and one on Honshu Island. Genetic diversity parameters such as allelic richness and gene diversity were significantly lower in the Kyushu group than the Honshu group. Furthermore, STRUCTURE analysis revealed that the two lineages were admixed in the western part of Honshu Island. Thus, although the phylogeographical structure of the species and hybridization dynamics among related species need to be evaluated in detail using several marker systems, the Kyusyu Island and Honshu Island populations should be considered as different conservation units, and the islands should be regarded as distinct seed transfer zones for C. jamasakura, especially when rapid assessments are required.

Seasonal changes in photosynthetic capacity, leaf nitrogen (N) content, leaf chlorophyll (Chl) content and leaf N allocation patterns in leaves of different ages in the evergreen understory shrub, Daphniphyllum humile Maxim, growing at a forest border and an understory site were studied. In current-year leaves at the understory site, the N and Rubisco contents increased from spring to autumn although their light-saturated photosynthetic rate at 22°C (P max 22 ) remained stable, indicating that their mesophyll conductance rates declined as they completed their development and/or that they invested increasing amounts of their resources in photosynthetic enzymes during this period. In contrast, seasonal changes in P max 22 in current-year leaves at the forest border site were correlated with changes in Rubisco content. In 1-year old leaves at the understory site, P max 22 and contents of Chl, leaf N, and Rubisco remained stable from spring to autumn, while these parameters decreased in 1-year-old forest border leaves, indicating that N may have been remobilized from shaded 1-year-old leaves to sunlit current-year leaves. When leaves senesced at the forest border site the Rubisco content decreased more rapidly than that of light-harvesting proteins such as LHCII, suggesting that N remobilization from Rubisco may be more efficient, possibly because Rubisco has greater N costs and is soluble, whereas the light-harvesting proteins are membrane components.

We surveyed the distribution of S-alleles in natural island populations of Prunus lannesiana var. speciosa sampled from seven sites on the Izu Peninsula and six Izu islands, Japan. The S-genotypes of sampled individuals were determined by Southern analysis of RFLPs generated by restriction enzyme digestion of genomic DNA, using cDNA of the S-RNase gene as a probe. All individuals were heterozygous, as expected under gametophytic self-incompatibility (GSI). Sixty-three S-alleles were observed in the species, but 12 private to the Izu Peninsula population seemed to be derived from related species, giving a total of 75. The estimated number of S-alleles in each population ranged from 26 to 62, and was inversely correlated with the respective population’s distance from the Izu Peninsula, the closest point in the mainland to the islands. This geographical cline in the estimated numbers of S-alleles suggests that gene flow to and from the distant island populations was less frequent, and that the studied species has migrated from the mainland to the Izu islands. The genetic relationship at the S-locus among populations also gave an “isolation by distance” pattern. The genetic differentiation at the S-locus among the populations was very low (FST = 0.014, p < 0.001). The number of S-alleles in the species did not seem to depend on genetic differences associated with population subdivisions. This might be due to the greater effective migration rates of S-alleles, as expected under balancing selection in GSI.

To identify and characterize lineage-specific genes of conifers, two sets of ESTs (with 12791 and 5902 ESTs, representing 5373 and 3018 gene transcripts, respectively) were generated from the Cupressaceae species Cryptomeria japonica and Chamaecyparis obtusa. These transcripts were compared with non-redundant sets of genes generated from Pinaceae species, other gymnosperms and angiosperms. About 6% of tentative unique genes (Unigenes) of C. japonica and C. obtusa had homologs in other conifers but not angiosperms, and about 70% had apparent homologs in angiosperms. The calculated GC contents of orthologous genes showed that GC contents of coniferous genes are likely to be lower than those of angiosperms. Comparisons of the numbers of homologous genes in each species suggest that copy numbers of genes may be correlated between diverse seed plants. This correlation suggests that the multiplicity of such genes may have arisen before the divergence of gymnosperms and angiosperms.

Summary Photoprotective responses during photosynthetic acclimation in Daphniphyllum humile Maxim, an evergreen understory shrub that grows in temperate deciduous forests, were examined in relation to changes in light availability and temperature caused by the seasonal dynamics of canopy leaf phenology. Gradual increases in irradiance in the understory from summer to autumn as overstory foliage senesced were accompanied by increased concentrations of xanthophyll cycle pigments (VAZ) in understory leaves. The chlorophyll (Chl) a/ b ratio in understory leaves also increased from summer to autumn, reflecting the change in ratio of the light-harvesting antenna to the reaction center. However, low temperatures following overstory leaf fall reduced Rubisco activity. In contrast, the photosynthetic capactiy of leaves of D. humile growing at the forest border, which was higher in summer than that of leaves of understory plants, decreased in autumn. In autumn, Fv/Fm ratios decreased and concentrations of zeaxanthin (Z) and especially antheraxanthin (A) increased in leaves of both forest-border and understory plants. Although VAZ was twice as high in leaves of forest-border than of understory plants, NPQ was similar in both. We conclude that leaves of understory plants are able to acclimate to seasonal changes in light and temperature by varying their photosynthetic and photoprotective functions, thereby taking advantage of the favorable light conditions caused by overstory leaf fall.

Xanthophyll rhodoxanthin, which is present in sun-exposed needles of certain gymnosperms in winter, may have a photoprotective role during long-term cold acclimation. To examine how cold acclimation processes vary within tree crowns and to examine putative correlations between xanthophyll cycle pigments (VAZ), rhodoxanthin and the water-water cycle in photoprotection, we monitored seasonal changes in the activities of two key antioxidant enzymes (ascorbate peroxidase (APX) and glutathione reductase (GR)), pigment composition and chlorophyll fluorescence parameters in sun and shade needles of crowns of the gymnosperm Cryptomeria japonica D. Don. Although APX and GR activities in both sun and shade needles were higher in winter than in summer when assayed at 20 degrees C, differences between seasons were less pronounced when enzymatic activities in summer and winter were assayed at 20 and 5 degrees C, respectively. These results suggest that increases in the potential activity of antioxidant enzymes in winter is an adaptation that helps counterbalance reductions in absolute enzyme activity caused by low temperature, and thus allows the photoprotective capacity of the water-water cycle in C. japonica to be maintained at a roughly constant value throughout the year. In shade needles, the concentration of VAZ increased in winter, but no rhodoxanthin accumulated. Photosynthetic activity was maintained in winter. In sun needles, however, the electron transport rate (ETR) and photochemical quenching (q(P)) decreased to their lowest values in December, just before the accumulation of rhodoxanthin, which coincided with the highest amount of VAZ. Changes in rhodoxanthin concentration mirrored changes in VAZ concentration from January to March. Winter values of ETR and q(P) were comparable with summer values after accumulation of rhodoxanthin, indicating that rhodoxanthin may play a more important role than the VAZ cycle in protecting the photosynthetic apparatus from photodamage in winter. Photosynthetic activity may be modulated, as a result of the interception of light by rhodoxanthin, to match the extent to which absorbed light energy can be utilized in winter when the VAZ cycle is unable to operate effectively because of low temperatures.

We measured horizontal and vertical gradients of light (rPPFD) along four first-order branches of a Pinus densiflora Sieb. & Zucc. crown, and compared variations in specific leaf area (SLA), needle nitrogen concentration (N), chlorophyll concentration (Chl) and photosynthetic capacity (i.e., maximum rate of carboxylation (V cmax )) along the two axes. The horizontal gradient of rPPFD along first-order branches was similar in magnitude to the vertical gradient of rPPFD from the upper to the lower crown. None of the measured parameters (i.e., SLA, N, Chl and V cmax ) were strictly proportional to rPPFD, although they were more or less correlated with light when data obtained for all of the crown were pooled (r 2 = 0.31-0.80). The slope of rPPFD against N on an area basis (N area ) for a branch in the middle of the crown orientated northward was significantly greater than the slope for a similar branch orientated southward. Horizontal variations were unrelated to age effects because measurements were all on 1-year-old needles. We conclude that factors other than light (i.e., orientation) may influence N allocation within branches. There was considerably less variation in the relationship of V cmax to N area (r 2 = 0.58) than in the relationship of V cmax to rPPFD (r 2 = 0.41). Fractional N distribution among components of the photosynthetic machinery was constant within the crown. Together with the relationships between rPPFD and N on a mass basis (r 2 = 0.80) and SLA and V cmax (r 2 = 0.60), these findings suggest that most light acclimation in P. densiflora occurs through changes in needle morphology (e.g., SLA) during development.

In flowering plants, flower organ identity is controlled by the ABC genes, including several MADS box genes. We present two MADS box genes of a conifer, Cryptomeria japonica D. Don. The genes, CjMADS1 and CjMADS2 ,w ere related to the angiosperm B function genes which determine the identities of petals and stamens. A phylogenetic analysis showed that these genes form a new clade outside the angiosperm B group, that is, PISTILLATA (PI )a nd APETALA3 (AP3) lineages. CjMADS1 had a PI-group specific motif and CjMADS2 had AP3-group specific motifs at the C terminal end, respectively. CjMADS1 was expressed in male strobili (or cones) throughout its development, while CjMADS2 was transiently expressed during male strobilus development. The specific expression in the male reproductive organ indicated that the B function is maintained in gymnosperms. Our cladistic analysis suggests that the gene duplication event which generated B function gene lineages predates the divergence of angiosperms and gymnosperms and that the gene duplication which produced the two genes of C. japonica occurred in an ancestral conifer species.