Genomic traces of Japanese malting barley breeding in two modern high-quality cultivars, 'Sukai Golden' and 'Sachiho Golden'

Two modern high-quality Japanese malting barley cultivars, 'Sukai Golden' and 'Sachiho Golden', were subjected to RNA-sequencing of transcripts extracted from 20-day-old immature seeds. Despite their close relation, 2,419 Sukai Golden-specific and 3,058 Sachiho Golden-specific SNPs were detected in comparison to the genome sequences of two reference cultivars: 'Morex' and 'Haruna Nijo'. Two single nucleotide polymorphism (SNP) clusters respectively showing the incorporation of (1) the barley yellow mosaic virus (BaYMV) resistance gene rym5 from six-row non-malting Chinese landrace Mokusekko 3 on the long arm of 3H, and (2) the anthocyanin-less ant2 gene from a two-row Dutch cultivar on the long arm of 2H were detected specifically in 'Sukai Golden'. Using 221 recombinant inbred lines of a cross between 'Ishukushirazu' and 'Nishinochikara', another BaYMV resistance rym3 gene derived from six-row non-malting Japanese cultivar 'Haganemugi' was mapped to a 0.4-cM interval on the proximal region of 5H. Haplotype analysis of progenitor accessions of the two modern malting cultivars revealed that rym3 of 'Haganemugi' was independently introduced into 'Sukai Golden' and 'Sachiho Golden'. Residual chromosome 5H segments of 'Haganemugi' surrounding rym3 were larger in 'Sukai Golden'. Available results suggest possibilities for malting quality improvement by minimizing residual segments surrounding rym3.

Molecular identification of a laccase that catalyzes the oxidative coupling of a hydroxycinnamic acid amide for hordatine biosynthesis in barley

Plants produce dimerized phenolic compounds as secondary metabolites. Hordatine A (HA), a dehydrodimer of p-coumaroylagmatine (pCA), is an antifungal compound accumulated at high levels in young barley (Hordeum vulgare) seedlings. The enzyme responsible for the oxidative dimerization of pCA, which is the final step of the hordatine biosynthetic pathway, has not been identified. In this study, we first verified the presence of this enzyme activity in the crude extract of barley seedlings. Because the enzyme activity was not dependent on H2 O2 , the responsible enzyme was not peroxidase, which was previously implicated in HA biosynthesis. The analysis of the dissection lines of wheat (Triticum aestivum) carrying aberrant barley 2H chromosomes detected HA in the wheat lines carrying the distal part of the 2H short arm. This chromosomal region contains two laccase genes (HvLAC1 and HvLAC2) that are highly expressed at the seedling stage and may encode enzymes that oxidize pCA during the formation of HA. Changes in the HvLAC transcript levels coincided with the changes in the HA biosynthesis-related enzyme activities in the crude extract and the HA content in barley seedlings. Moreover, HvLAC genes were heterologously expressed in Nicotiana benthamiana leaves and in bamboo (Phyllostachys nigra) suspension cells and HA biosynthetic activities were detected in the crude extract of transformed N. benthamiana leaves and bamboo suspension cells. The HA formed by the enzymatic reaction had the same stereo-configuration as the naturally occurring HA. These results demonstrate that HvLAC enzymes mediate the oxidative coupling of pCA during HA biosynthesis.

A bifurcated palea mutant infers functional differentiation of WOX3 genes in flower and leaf morphogenesis of barley

Barley (Hordeum vulgare) is the fourth most highly produced cereal in the world after wheat, rice and maize and is mainly utilized as malts and for animal feed. Barley, a model crop of the tribe Triticeae, is important in comparative analyses of Poaceae. However, molecular understanding about the developmental processes is limited in barley. Our previous work characterized one of two WUSCHEL-RELATED HOMEOBOX 3 (WOX3) genes present in the barley genome: NARROW LEAFED DWARF1 (NLD1). We demonstrated that NLD1 plays a pivotal role in the development of lateral organs. In the present study, we describe a bifurcated palea (bip) mutant of barley focusing on flower and leaf phenotypes. The palea in the bip mutant was split into two and develop towards inside the lemma surrounding the carpels and anthers. The bip mutant is devoid of lodicules, which develop in a pair at the base of the stamen within the lemma in normal barley. bip also exhibited malformations in leaves, such as narrow leaf due to underdeveloped leaf-blade width, and reduced trichome density. Map-based cloning and expression analysis indicated that BIP is identical to another barley WOX3 gene, named HvWOX3. The bip nld1 double mutant presented a more severe reduction in leaf-blade width and number of trichomes. By comparing the phenotypes and gene expression patterns of various WOX3 mutants, we concluded that leaf bilateral outgrowth and trichome development are promoted by both NLD1 and HvWOX3, but that HvWOX3 serves unique and pivotal functions in barley development that differ from those of NLD1.

Mutations in a�Golden2-Like�Gene Cause Reduced Seed Weight in�Barley�albino lemma 1�Mutants

The albino lemma 1 (alm1) mutants of barley (Hordeum vulgare L.) exhibit obvious chlorophyll-deficient hulls. Hulls are seed-enclosing tissues on the spike, consisting of the lemma and palea. The alm1 phenotype is also expressed in the pericarp, culm nodes and basal leaf sheaths, but leaf blades and awns are normal green. A single recessive nuclear gene controls tissue-specific alm1 phenotypic expression. Positional cloning revealed that the ALM1 gene encodes a Golden 2-like (GLK) transcription factor, HvGLK2, belonging to the GARP subfamily of Myb transcription factors. This finding was validated by genetic evidence indicating that all 10 alm1 mutants studied had a lesion in functionally important regions of HvGLK2, including the three alpha-helix domains, an AREAEAA motif and the GCT box. Transmission electron microscopy revealed that, in lemmas of the alm1.g mutant, the chloroplasts lacked thylakoid membranes, instead of stacked thylakoid grana in wild-type chloroplasts. Compared with wild type, alm1.g plants showed similar levels of leaf photosynthesis but reduced spike photosynthesis by 34%. The alm1.g mutant and the alm1.a mutant showed a reduction in 100-grain weight by 15.8% and 23.1%, respectively. As in other plants, barley has HvGLK2 and a paralog, HvGLK1. In flag leaves and awns, HvGLK2 and HvGLK1 are expressed at moderate levels, but in hulls, HvGLK1 expression was barely detectable compared with HvGLK2. Barley alm1/Hvglk2 mutants exhibit more severe phenotypes than glk2 mutants of other plant species reported to date. The severe alm1 phenotypic expression in multiple tissues indicates that HvGLK2 plays some roles that are nonredundant with HvGLK1.

Regulation of the plastochron by three many-noded dwarf genes in barley

The plastochron, the time interval between the formation of two successive leaves, is an important determinant of plant architecture. We genetically and phenotypically investigated many-noded dwarf (mnd) mutants in barley. The mnd mutants exhibited a shortened plastochron and a decreased leaf blade length, and resembled previously reported plastochron1 (pla1), pla2, and pla3 mutants in rice. In addition, the maturation of mnd leaves was accelerated, similar to pla mutants in rice. Several barley mnd alleles were derived from three genes-MND1, MND4, and MND8. Although MND4 coincided with a cytochrome P450 family gene that is a homolog of rice PLA1, we clarified that MND1 and MND8 encode an N-acetyltransferase-like protein and a MATE transporter-family protein, which are respectively orthologs of rice GW6a and maize BIGE1 and unrelated to PLA2 or PLA3. Expression analyses of the three MND genes revealed that MND1 and MND4 were expressed in limited regions of the shoot apical meristem and leaf primordia, but MND8 did not exhibit a specific expression pattern around the shoot apex. In addition, the expression levels of the three genes were interdependent among the various mutant backgrounds. Genetic analyses using the double mutants mnd4mnd8 and mnd1mnd8 indicated that MND1 and MND4 regulate the plastochron independently of MND8, suggesting that the plastochron in barley is controlled by multiple genetic pathways involving MND1, MND4, and MND8. Correlation analysis between leaf number and leaf blade length indicated that both traits exhibited a strong negative association among different genetic backgrounds but not in the same genetic background. We propose that MND genes function in the regulation of the plastochron and leaf growth and revealed conserved and diverse aspects of plastochron regulation via comparative analysis of barley and rice.

Identification of methoxylchalcones produced in response to CuCl2 treatment and pathogen infection in barley

Changes in specialized metabolites were analyzed in barley (Hordeum vulgare) leaves treated with CuCl₂ solution as an elicitor. LC-MS analysis of the CuCl₂-treated leaves showed the induced accumulation of three compounds. Among them, two were purified by silica gel and ODS column chromatography and preparative HPLC and were identified as 2',3,4,4',6'-pentamethoxychalcone and 2'-hydroxy-3,4,4',6'-tetramethoxychalcone by spectroscopic analyses. The remaining compound was determined as 12-oxo-phytodienoic acid (OPDA), a major oxylipin in plants, by comparing its spectrum and retention time from LC-MS/MS analysis with those of the authentic compound. The accumulation of these compounds was reproduced in leaves inoculated with Bipolaris sorokiniana, the causal agent of spot blotch of the Poaceae species. This inoculation increased the amounts of other oxylipins, including jasmonic acid (JA), JA-Ile, 9-oxooctadeca-10,12-dienoic acid (9-KODE), and 13-oxooctadeca-9,11-dienoic acid (13-KODE). The treatments of the barley leaves with JA and OPDA induced the accumulation of methoxylchalcones, but treatment with 9-KODE did not. These methoxylchalcones inhibited conidial germination of B. sorokiniana and Fusarium graminearum, thereby indicating that these compounds possessed antifungal activity. Consequently, they are considered to be involved in the chemical defense processes as phytoalexins in barley. Accumulation of methoxylchalcones in response to JA treatment was observed in all seven barley cultivars tested, but was not detected in other wild Hordeum species, wheat, and rice, thus indicating that their production was specific to cultivated barley.

Phylogenetic analysis of the Si7PPO gene in foxtail millet, Setaria italica, provides further evidence for multiple origins of the negative phenol color reaction phenotype

To elucidate the diversity and evolution of the Si7PPO gene that controls phenol color reaction (Phr) in foxtail millet, Setaria italica, we analyzed sequence polymorphisms of the Si7PPO gene in 39 accessions consisting of foxtail millet landraces (32 accessions) and their wild ancestor ssp. viridis (seven accessions) collected from various regions in Europe and Asia. The accessions included wild type (positive Phr) and three different types of loss-of-function phenotype (negative Phr), "stop codon type", "TE1-insertion type" and "6-bp duplication type", found in our previous study. We constructed a phylogenetic tree of the gene and found that accessions with positive Phr showed higher genetic diversity at the nucleotide sequence level. We also found that the three different loss-of-function types formed different clusters, suggesting that landraces with negative Phr have multiple origins from three different lineages including both landrace and ssp. viridis accessions with positive Phr.

Biosynthesis of Phenylamide Phytoalexins in Pathogen-Infected Barley

Phytoalexins are inducible antimicrobial metabolites in plants, and have been indicated to be important for the rejection of microbial infection. HPLC analysis detected the induced accumulation of three compounds 1–3 in barley (Hordeum vulgare) roots infected by Fusarium culmorum, the causal agent of Fusarium root rot. Compounds 1–3 were identified as cinnamic acid amides of 9-hydroxy-8-oxotryptamine, 8-oxotryptamine, and (1H-indol-3-yl)methylamine, respectively, by spectroscopic analysis. Compounds 1 and 2 had been previously reported from wheat, whereas 3 was an undescribed compound. We named 1–3 as triticamides A–C, respectively, because they were isolated from barley and wheat, which belong to the Triticeae tribe. These compounds showed antimicrobial activities, indicating that triticamides function as phytoalexins in barley. The administration of deuterium-labeled N-cinnamoyl tryptamine (CinTry) to barley roots resulted in the effective incorporation of CinTry into 1 and 2, which suggested that they were synthesized through the oxidation of CinTry. Nine putative tryptamine hydroxycinnamoyl transferase (THT)-encoding genes (HvTHT1–HvTHT9) were identified by database search on the basis of homology to known THT gene sequences from rice. Since HvTHT7 and HvTHT8 had the same sequences except one base, we measured their expression levels in total by RT-qPCR. HvTHT7/8 were markedly upregulated in response to infection by F. culmorum. The HvTHT7 and HvTHT8 enzymes preferred cinnamoyl- and feruloyl-CoAs as acyl donors and tryptamine as an acyl acceptor, and (1H-indol-3-yl)methylamine was also accepted as an acyl acceptor. These findings suggested that HvTHT7/8 are responsible for the induced accumulation of triticamides in barley.

Identification of phenylamide phytoalexins and characterization of inducible phenylamide metabolism in wheat

Changes in specialized metabolites were analyzed in wheat leaves inoculated with Bipolaris sorokiniana, the causal agent of spot blotch of Poaceae species. HPLC analysis detected the accumulation of six compounds in B. sorokiniana-infected leaves. Of these, we purified two compounds by silica gel and ODS column chromatography and preparative HPLC, and identified them as cinnamic acid amides, N-cinnamoyl-9-hydroxy-8-oxotryptamine and N-cinnamoyl-8-oxotryptamine, by spectroscopic analyses. The remaining four compounds were predicted to be p-coumaric acid amides of hydroxyputrescine, hydroxyagmatine, hydroxydehydroagmatine, and agmatine by mass spectrometry. The accumulation of two cinnamic acid amides was also induced by Fusarium graminearum infection, and by treatment with CuCl₂, jasmonic acid, and isopentenyladenine. Antifungal activity of these amides was shown by inhibition of conidial germination and germ tube elongation of F. graminearum and Alternaria brassicicola, indicating that they act as phytoalexins. The accumulation of these amides also detected in barley leaves treated with CuCl₂. We examined the accumulation of 25 phenylamides in B. sorokiniana-infected wheat leaves using LC-MS/MS. Hydroxycinnamic acid amides of tryptamine, serotonin, putrescine, and agmatine, were induced after infection with B. sorokiniana. Thus, the induced accumulation of two groups of phenylamides, cinnamic acid amides with indole amines, and p-coumaric acid amides with putrescine and agmatine related amines, represents a major metabolic response of wheat to pathogen infection.

Genebank genomics highlights the diversity of a global barley collection

Genebanks hold comprehensive collections of cultivars, landraces and crop wild relatives of all major food crops, but their detailed characterization has so far been limited to sparse core sets. The analysis of genome-wide genotyping-by-sequencing data for almost all barley accessions of the German ex situ genebank provides insights into the global population structure of domesticated barley and points out redundancies and coverage gaps in one of the world's major genebanks. Our large sample size and dense marker data afford great power for genome-wide association scans. We detect known and novel loci underlying morphological traits differentiating barley genepools, find evidence for convergent selection for barbless awns in barley and rice and show that a major-effect resistance locus conferring resistance to bymovirus infection has been favored by traditional farmers. This study outlines future directions for genomics-assisted genebank management and the utilization of germplasm collections for linking natural variation to human selection during crop evolution.

Evolutionary changes in defensive specialized metabolism in the genus Hordeum

Plants have developed defensive specialized metabolites over the course of evolution. In the genus Hordeum, which includes the important cereal crop barley, specialized metabolites such as hordatines, benzoxazinones, and gramine have been identified. Hordeum species are classified into four clades, H, Xu, Xa, and I. The presence or absence of defensive specialized metabolites was analyzed in representative Hordeum species that included all of the four clades. In the H clade, Hordeum vulgare accumulated hordatines but not benzoxazinones, whereas H. bulbosum accumulated neither compound. Some accessions in the H clade accumulated gramine. Species in the clades I and Xa accumulated benzoxazinones without hordatines. In H. murinum, a Xu clade species, neither hordatines nor benzoxazinones were detected. Two hitherto undescribed compounds were found to commonly accumulate in H. bulbosum in the H clade and H. murinum in the Xu clade. On the basis of spectroscopic analyses, they were identified as dehydrodimers of feruloylagmatine and were designated murinamides A and B. Radical coupling reactions with feruloylagmatine as a substrate by peroxidase afforded murinamides A and B. These compounds showed antifungal activities against Bipolaris sorokiniana and Fusarium asiaticum, indicating their defensive roles. Because hordatines are also dehydrodimers of hydroxycinnamic acid amides (HCAAs) of agmatine, both the H and Xu clade species are considered to accumulate the same class of compounds. Thus, when the H/Xu clades split from the I/Xa clades during evolution, the defensive metabolites shifted from benzoxazinones to dehydrodimers of agmatine HCAAs plus gramine in the H/Xu clades.

Distribution of the tryptophan pathway-derived defensive secondary metabolites gramine and benzoxazinones in Poaceae

The Poaceae is a large taxonomic group consisting of approximately 12,000 species and is classified into 12 subfamilies. Gramine and benzoxazinones (Bxs), which are biosynthesized from the tryptophan pathway, are well-known defensive secondary metabolites in the Poaceae. We analyzed the presence or absence of garamine and Bxs in 64 species in the Poaceae by LC-MS/MS. We found that Hordeum brachyantherum and Hakonechloa macra accumulated gramine, but the presence of gramine was limited to small groups of species. We also detected Bxs in four species in the Pooideae and six species in the Panicoideae. In particular, four species in the Paniceae tribe in Panicoideae accumulaed Bxs, indicating that this tribe is a center of the Bx distribution. Bxs were absent in the subfamilies other than Pooideae and Panicoideae. These findings provide an overview of biased distribution of gramine and Bxs in Poaceae species.

A Homolog of Blade-On-Petiole 1 and 2 (BOP1/2) Controls Internode Length and Homeotic Changes of the Barley Inflorescence

Inflorescence architecture in small-grain cereals has a direct effect on yield and is an important selection target in breeding for yield improvement. We analyzed the recessive mutation laxatum-a (lax-a) in barley (Hordeum vulgare), which causes pleiotropic changes in spike development, resulting in (1) extended rachis internodes conferring a more relaxed inflorescence, (2) broadened base of the lemma awns, (3) thinner grains that are largely exposed due to reduced marginal growth of the palea and lemma, and (4) and homeotic conversion of lodicules into two stamenoid structures. Map-based cloning enforced by mapping-by-sequencing of the mutant lax-a locus enabled the identification of a homolog of BLADE-ON-PETIOLE1 (BOP1) and BOP2 as the causal gene. Interestingly, the recently identified barley uniculme4 gene also is a BOP1/2 homolog and has been shown to regulate tillering and leaf sheath development. While the Arabidopsis (Arabidopsis thaliana) BOP1 and BOP2 genes act redundantly, the barley genes contribute independent effects in specifying the developmental growth of vegetative and reproductive organs, respectively. Analysis of natural genetic diversity revealed strikingly different haplotype diversity for the two paralogous barley genes, likely affected by the respective genomic environments, since no indication for an active selection process was detected.

Barley NARROW LEAFED DWARF1 encoding a WUSCHEL-RELATED HOMEOBOX 3 (WOX3) regulates the marginal development of lateral organs

Barley (Hordeum vulgare L.) is the fourth most-produced cereal in the world and is mainly utilized as animal feed and malts. Recently barley attracts considerable attentions as healthy food rich in dietary fiber. However, limited knowledge is available about developmental aspects of barley leaves. In the present study, we investigated barley narrow leafed dwarf1 (nld1) mutants, which exhibit thin leaves accompanied by short stature. Detailed histological analysis revealed that leaf marginal tissues, such as sawtooth hairs and sclerenchymatous cells, were lacked in nld1, suggesting that narrowed leaf of nld1 was attributable to the defective development of the marginal regions in the leaves. The defective marginal developments were also appeared in internodes and glumes in spikelets. Map-based cloning revealed that NLD1 encodes a WUSCHEL-RELATED HOMEOBOX 3 (WOX3), an ortholog of the maize NARROW SHEATH genes. In situ hybridization showed that NLD1 transcripts were localized in the marginal edges of leaf primordia from the initiating stage. From these results, we concluded that NLD1 plays pivotal role in the increase of organ width and in the development of marginal tissues in lateral organs in barley.

Barley Ant17, encoding flavanone 3-hydroxylase (F3H), is a promising target locus for attaining anthocyanin/proanthocyanidin-free plants without pleiotropic reduction of grain dormancy

Preharvest sprouting is a serious problem in grain crop production because it causes quality deterioration and economic losses. It is well known that grain colour is closely associated with grain dormancy in wheat; white-grained lines without accumulating proanthocyanidins in testa tend to be more susceptible to preharvest sprouting than red ones. All available white-grained wheat lines are restricted to triple recessive mutations at the R loci (R-A1, R-B1, and R-D1), but barley is known to have 11 independent loci conferring the proanthocyanidin-free grain phenotype. In this study, we evaluated the dormancy levels of anthocyanin/proanthocyanidin-free ant17 mutants. Three ant17 mutants showed the same levels of dormancy as their respective wild types. Sequencing of three independent ant17 alleles detected a point mutation within the coding regions of flavanone-3-hydroxylase (F3H), which are predicted to cause a premature stop codon at different sites. The F3H locus completely cosegregated with the Ant17 position on the chromosome arm 2HL. Expression of the barley F3H gene was observed in pigmented tissues, but not in nonpigmented roots and stems. This result indicates that wheat F3H may be a promising new target locus for breeding white-grained lines with a practical level of preharvest sprouting resistance.

Wholegrain barley β-glucan fermentation does not improve glucose tolerance in rats fed a high-fat diet

Fermentation of oat and barley β-glucans is believed to mediate in part their metabolic health benefits, but the exact mechanisms remain unclear. In this study, we sought to test the hypothesis that barley β-glucan fermentation raises circulating incretin hormone levels and improves glucose control, independent of other grain components. Male Sprague-Dawley rats (n = 30) were fed a high-fat diet for 6 weeks and then randomly allocated to 1 of 3 dietary treatments for 2 weeks. The low- (LBG, 0% β-glucan) and high- (HBG, 3% β-glucan) β-glucan diets contained 25% wholegrain barley and similar levels of insoluble dietary fiber, available carbohydrate, and energy. A low-fiber diet (basal) was included for comparison. Immediately prior to the dietary intervention, gastric emptying rate (using the (13)C-octanoic breath test) and postprandial glycemic response of each diet were determined. At the end of the study, circulating gut hormone levels were determined; and a glucose tolerance test was performed. The rats were then killed, and indices of cecal fermentation were assessed. Diet did not affect live weight; however, the HBG diet, compared to basal and LBG, reduced food intake, tended to slow gastric emptying, increased cecal digesta mass and individual and total short-chain fatty acid pools, and lowered digesta pH. In contrast, circulating levels of glucose, insulin, gastric-inhibitory peptide, and glucagon-like peptide-1, and glucose tolerance were unaffected by diet. In conclusion, wholegrain barley β-glucan suppressed feed intake and increased cecal fermentation but did not improve postprandial glucose control or insulin sensitivity.

A SHORT INTERNODES (SHI) family transcription factor gene regulates awn elongation and pistil morphology in barley

The awn, an apical extension from the lemma of the spikelet, plays important roles in seed dispersal, burial, and photosynthesis. Barley typically has long awns, but short-awn variants exist. The short awn 2 (lks2) gene, which produces awns about 50% shorter than normal, is a natural variant that is restricted to Eastern Asia. Positional cloning revealed that Lks2 encodes a SHI-family transcription factor. Allelism tests showed that lks2 is allelic to unbranched style 4 (ubs4) and breviaristatum-d (ari-d), for which the phenotypes are very short awn and sparse stigma hairs. The gene identity was validated by 25 mutant alleles with lesions in the Lks2 gene. Of these, 17 affected either or both conserved regions: the zinc-binding RING-finger motif and the IGGH domain. Lks2 is highly expressed in awns and pistils. Histological observations of longitudinal awn sections showed that the lks2 short-awn phenotype resulted from reduced cell number. Natural variants of lks2 were classified into three types, but all shared a single-nucleotide polymorphism (SNP) that causes a proline-to-leucine change at position 245 in the IGGH domain. All three lks2 natural variants were regarded as weak alleles because their awn and pistil phenotypes are mild compared with those of the 25 mutant alleles. Natural variants of lks2 found in the east of China and the Himalayas had considerably different sequences in the regions flanking the critical SNP, suggesting independent origins. The available results suggest that the lks2 allele might have a selective advantage in the adaptation of barley to high-precipitation areas of Eastern Asia.

Functional characterization of barley betaglucanless mutants demonstrates a unique role for CslF6 in (1,3;1,4)-β-D-glucan biosynthesis

(1,3;1,4)-β-D-glucans (mixed-linkage glucans) are found in tissues of members of the Poaceae (grasses), and are particularly high in barley (Hordeum vulgare) grains. The present study describes the isolation of three independent (1,3;1,4)-β-D-glucanless (betaglucanless; bgl) mutants of barley which completely lack (1,3;1,4)-β-D-glucan in all the tissues tested. The bgl phenotype cosegregates with the cellulose synthase like HvCslF6 gene on chromosome arm 7HL. Each of the bgl mutants has a single nucleotide substitution in the coding region of the HvCslF6 gene resulting in a change of a highly conserved amino acid residue of the HvCslF6 protein. Microsomal membranes isolated from developing endosperm of the bgl mutants lack detectable (1,3;1,4)-β-D-glucan synthase activity indicating that the HvCslF6 protein is inactive. This was confirmed by transient expression of the HvCslF6 cDNAs in Nicotiana benthamiana leaves. The wild-type HvCslF6 gene directed the synthesis of high levels of (1,3;1,4)-β-D-glucans, whereas the mutant HvCslF6 proteins completely lack the ability to synthesize (1,3;1,4)-β-D-glucans. The fine structure of the (1,3;1,4)-β-D-glucan produced in the tobacco leaf was also very different from that found in cereals having an extremely low DP3/DP4 ratio. These results demonstrate that, among the seven CslF and one CslH genes present in the barley genome, HvCslF6 has a unique role and is the key determinant controlling the biosynthesis of (1,3;1,4)-β-D-glucans. Natural allelic variation in the HvCslF6 gene was found predominantly within introns among 29 barley accessions studied. Genetic manipulation of the HvCslF6 gene could enable control of (1,3;1,4)-β-D-glucans in accordance with the purposes of use.

Duplicate polyphenol oxidase genes on barley chromosome 2H and their functional differentiation in the phenol reaction of spikes and grains

Polyphenol oxidases (PPOs) are copper-containing metalloenzymes encoded in the nucleus and transported into the plastids. Reportedly, PPOs cause time-dependent discoloration (browning) of end-products of wheat and barley, which impairs their appearance quality. For this study, two barley PPO homologues were amplified using PCR with a primer pair designed in the copper binding domains of the wheat PPO genes. The full-lengths of the respective PPO genes were cloned using a BAC library, inverse-PCR, and 3'-RACE. Linkage analysis showed that the polymorphisms in PPO1 and PPO2 co-segregated with the phenol reaction phenotype of awns. Subsequent RT-PCR experiments showed that PPO1 was expressed in hulls and awns, and that PPO2 was expressed in the caryopses. Allelic variation of PPO1 and PPO2 was analysed in 51 barley accessions with the negative phenol reaction of awns. In PPO1, amino acid substitutions of five types affecting functionally important motif(s) or C-terminal region(s) were identified in 40 of the 51 accessions tested. In PPO2, only one mutant allele with a precocious stop codon resulting from an 8 bp insertion in the first exon was found in three of the 51 accessions tested. These observations demonstrate that PPO1 is the major determinant controlling the phenol reaction of awns. Comparisons of PPO1 single mutants and the PPO1PPO2 double mutant indicate that PPO2 controls the phenol reaction in the crease on the ventral side of caryopses. An insertion of a hAT-family transposon in the promoter region of PPO2 may be responsible for different expression patterns of the duplicate PPO genes in barley.

Studies on sodium bypass flow in lateral rootless mutants lrt1 and lrt2, and crown rootless mutant crl1 of rice (Oryza sativa L.)

An apoplastic pathway, the so-called bypass flow, is important for Na+ uptake in rice (Oryza sativa L.) under saline conditions; however, the precise site of entry is not yet known. We report the results of our test of the hypothesis that bypass flow of Na+ in rice occurs at the site where lateral roots emerge from the main roots. We investigated Na+ uptake and bypass flow in lateral rootless mutants (lrt1, lrt2), a crown rootless mutant (crl1), their wild types (Oochikara, Nipponbare and Taichung 65, respectively) and in seedlings of rice cv. IR36. The results showed that shoot Na+ concentration in lrt1, lrt2 and crl1 was lower (by 20-23%) than that of their wild types. In contrast, the bypass flow quantified using trisodium-8-hydroxy-1,3,6-pyrenetrisulphonic acid (PTS) was significantly increased in the mutants, from an average of 1.1% in the wild types to 3.2% in the mutants. Similarly, bypass flow in shoots of IR36 where the number of lateral and crown roots had been reduced through physical and hormonal manipulations was dramatically increased (from 5.6 to 12.5%) as compared to the controls. The results suggest that the path of bypass flow in rice is not at the sites of lateral root emergence.

Barley grain with adhering hulls is controlled by an ERF family transcription factor gene regulating a lipid biosynthesis pathway

In contrast to other cereals, typical barley cultivars have caryopses with adhering hulls at maturity, known as covered (hulled) barley. However, a few barley cultivars are a free-threshing variant called naked (hulless) barley. The covered/naked caryopsis is controlled by a single locus (nud) on chromosome arm 7HL. On the basis of positional cloning, we concluded that an ethylene response factor (ERF) family transcription factor gene controls the covered/naked caryopsis phenotype. This conclusion was validated by (i) fixation of the 17-kb deletion harboring the ERF gene among all 100 naked cultivars studied; (ii) two x-ray-induced nud alleles with a DNA lesion at a different site, each affecting the putative functional motif; and (iii) gene expression strictly localized to the testa. Available results indicate the monophyletic origin of naked barley. The Nud gene has homology to the Arabidopsis WIN1/SHN1 transcription factor gene, whose deduced function is control of a lipid biosynthesis pathway. Staining with a lipophilic dye (Sudan black B) detected a lipid layer on the pericarp epidermis only in covered barley. We infer that, in covered barley, the contact of the caryopsis surface, overlaid with lipids to the inner side of the hull, generates organ adhesion.

Saturated humidity accelerates lateral root development in rice (Oryza sativa L.) seedlings by increasing phloem-based auxin transport

Auxin transport plays a significant role modifying plant growth and development in response to environmental signals such as light and gravity. However, the effect of humidity on auxin transport is rarely documented. It is shown here that the transport of labelled indole-3-acetic acid (IAA) from the shoot to the root is accelerated in rice (Oryza sativa L. ssp. indica cv. IR8) seedlings grown under saturated humidity (SH-seedlings) compared with plants grown under normal humidity (NH-seedlings). The development of lateral roots in SH-seedlings was greatly enhanced compared with NH-seedlings. Removal of the shoot from SH-seedlings reduced the density of lateral roots, and the application of IAA to the cut stem restored the lateral root density, while the decapitation of NH-seedlings did not alter lateral root development. Phloem-based auxin transport appeared responsible for enhanced lateral root formation in SH-seedlings since (i) the rate of IAA transport from the shoot to the root tip was greater than 3.5 cm h-1 and (ii) naphthylphthalamic acid (NPA)-induced reduction of polar auxin transport in the shoot did not influence the number of lateral roots in SH-seedlings. It is proposed that high humidity conditions accelerate the phloem-based transport of IAA from the leaf to the root, resulting in an increase in the number of lateral roots.

Identifying the genome of wood barley Hordelymus europaeus (Poaceae: Triticeae)

Wood barley, Hordelymus europaeus, was compared with other Triticeae species by Southern and fluorescence in situ hybridisation using total genomic DNA and repetitive sequences as probes. On Southern blots, the total genomic probe from H. europaeus hybridised strongly to DNA of its own species and to Leymus and Psathyrostachys, indicating the presence of Ns genome in H. europaeus. Furthermore, the total genomic probe from P. fragilis hybridised to DNA of H. europaeus as much as to all of the Psathyrostachys and Leymus species examined. Ns genome-specific DNA sequences isolated from L. mollis (pLmIs1, pLmIs44 and pLmIs53) hybridised essentially to H. europaeus and all of the species of Leymus and Psathyrostachys. Chromosomal localization of these clones on H. europaeus confirmed the presence of Ns genome-specific DNA on all chromosomes, indiscriminately. Under moderate hybridisation stringency the Ns genome-specific probes, together with repetitive sequences pTa71 and pAesKB7, produced species-specific RFLP banding profiles on Southern blots. A phenetic tree based on these profiles revealed a distinct Ns species cluster within the Triticeae, represented by Leymus and Psathyrostachys species. Hordelymus europaeus belonged to this Ns cluster. Chromosomal mapping of the 18S-25S and the 5S ribosomal genes, together with the repetitive sequence pLrTaiI, corroborated that H. europaeus was most probably related to Leymus, especially the European/Eurasian members of sect. Leymus. In an attempt to identify the genome of H. europaeus, different approaches were employed; the results clearly showed that wood barley had the Ns basic genome and nothing else.

Involvement of ARM2 in the uptake of indole-3-butyric acid in rice (Oryza sativa L.) roots

Auxin influx carriers are involved in auxin transport and plant development. Here we show that the mutant of rice (Oryza sativa L. ssp. indica cv IR8) arm2 is defective in the uptake of the naturally occurring auxin indole-3-butyric acid (IBA). The acropetal and basipetal transport of IBA is reduced in arm2 roots compared with wild type. In contrast, arm2 roots are normal with respect to uptake and transport of indole-3-acetic acid (IAA). Furthermore, arm2 roots are resistant to IBA but respond normally to IAA. The mutant analysis of arm2 indicates the presence of an influx carrier system for IBA in rice roots.

Ancestry of American polyploid Hordeum species with the I genome inferred from 5S and 18S-25S rDNA

BACKGROUND AND AIMS

The genus Hordeum exists at three ploidy levels (2x, 4x and 6x) and presents excellent material for investigating the patterns of polyploid evolution in plants. Here the aim was to clarify the ancestry of American polyploid species with the I genome. *

METHODS

Chromosomal locations of 5S and 18S-25S ribosomal RNA genes were determined by fluorescence in situ hybridization (FISH). In both polyploid and diploid species, variation in 18S-25S rDNA repeated sequences was analysed by the RFLP technique. *

KEY RESULTS

Six American tetraploid species were divided into two types that differed in the number of rDNA sites and RFLP profiles. Four hexaploid species were similar in number and location of both types of rDNA sites, but the RFLP profiles of 18S-25S rDNA revealed one species, H. arizonicum, with a different ancestry. *

CONCLUSIONS

Five American perennial tetraploid species appear to be alloploids having the genomes of an Asian diploid H. roshevitzii and an American diploid species. The North American annual tetraploid H. depressum is probably a segmental alloploid combining the two closely related genomes of American diploid species. A hexaploid species, H. arizonicum, involves a diploid species, H. pusillum, in its ancestry; both species share the annual growth habit and are distributed in North America. Polymorphisms of rDNA sites detected by FISH and RFLP analyses provide useful information to infer the phylogenetic relationships of I-genome Hordeum species because of their highly conserved nature during polyploid evolution.

Defects in root development and gravity response in the aem1 mutant of rice are associated with reduced auxin efflux

The phytohormone auxin is involved in the regulation of a variety of developmental processes. In this report, we describe how the processes of lateral root and root hair formations and root gravity response in rice are controlled by auxin. We use a rice mutant aem1 (auxin efflux mutant) because the mutant is defective in these characters. The aem1 line was originally isolated as a short lateral root mutant, but we found that the mutant has a defect in auxin efflux in roots. The acropetal and basipetal indole-3-acetic acid (IAA) transports were reduced in aem1 roots compared to wild type (WT). Furthermore, gravitropic bending as well as efflux of radioactive IAA was impaired in the mutant roots. We also propose a unique distribution of endogenous IAA in aem1 roots. An immunoassay revealed a 4-fold-endogenous IAA content in the aem1 roots compared to WT, and the application of IAA to the shoot of WT seedlings mimicked the short lateral root phenotype of aem1, suggesting that the high content of IAA in aem1 roots impaired the elongation of lateral roots. However, the high level of IAA in aem1 roots contradicts the auxin requirement for root hair formation in the epidermis of mutant roots. Since the reduced development in root hairs of aem1 roots was rescued by exogenous auxin, the auxin level in the epidermis is likely to be sub-optimum in aem1 roots. This discrepancy can be solved by the ideas that IAA level is higher in the stele and lower in the epidermis of aem1 roots compared to WT and that the unique distribution of IAA in aem1 roots is induced by the defect in auxin efflux. All these results suggest that AEM1 may encode a component of auxin efflux carrier in rice and that the defects in lateral roots, root hair formation and root gravity response in aem1 mutant are due to the altered auxin efflux in roots.

Cytokinin inhibits lateral root initiation but stimulates lateral root elongation in rice (Oryza sativa)

Research in lateral root (LR) development mainly focuses on the role of auxin. This article reports the effect of cytokinins (kinetin and trans-zeatin) on LR formation in rice (Oryza sativa L.). Our results showed that cytokinin has an inhibitory effect on LR initiation and stimulatory effect on LR elongation. Both KIN and ZEA at a concentration of 1 microM and above completely inhibited lateral root primordium (LRP) formation. The inhibitory effect of cytokinin on LR initiation required a continuous presence of KIN or ZEA in the growth solution. Cytokinin did not show any inhibitory effect on LR emergence from the seminal root once LRPs had been formed. The LRPs that developed in cytokinin-free solution can emerge normally in the solution containing inhibitory concentration (1 microM) of KIN and ZEA. The KIN and ZEA treatment dramatically stimulated LR elongation at all the concentrations tested. Maximum LR elongation was observed at a concentration of 0.01 microM KIN and 0.001 microM ZEA. The epidermal cell length increased significantly in LRs of cytokinin treated seedlings compared to those of untreated control. This result indicates that the stimulation of LR elongation by cytokinin is due to increased cell length. Exogenously applied auxin counteracted the effect of cytokinin on LR initiation and LR elongation, suggesting that cytokinin acts on LR elongation through an auxin dependent pathway.

Molecular cytogenetic identification of nullisomy 5B induced homoeologous recombination between wheat chromosome 5D and barley chromosome 5H

Chromosome 5H of Hordeum vulgare 'New Golden' (NG) carries a gene(s) that accelerates heading in a wheat background. To introduce the early heading gene(s) of NG barley into the wheat genome, we attempted to induce homoeologous recombination between wheat and NG 5H chromosomes by 5B nullisomy. A nullisomic 5B, trisomic 5A, monosomic 5H plant (2n = 42) was produced from systematic crosses between aneuploid stocks of wheat group 5 chromosomes. A total of 656 F2 plants produced by self-fertilization were screened for recombinants by a PCR assay with 3 5H-specific amplicon markers. Twelve plants (1.8%) were selected as putative wheat-barley 5H recombinants. Five of them were inviable or sterile and the remaining 7 were fertile and subjected to the progeny test. Cytological analyses using fluorescence in situ hybridization and C-banding revealed that 6 of the 7 progeny lines are true homoeologous recombinants between the long arms of chromosomes 5D and 5H, but that the other one was not a recombinant having an aberrant barley telosome. The 6 cytologically confirmed recombinant lines included only 2 types (3 lines each), which were reciprocal products derived from exchanges at the same distal interval defined by two flanking markers. One type had a small 5HL segment translocated to the 5DL terminal, and the other type had a small terminal 5DL segment translocated to the 5HL terminal. In the latter type, the physical length of translocated barley segments slightly differed among lines. Homoeologous recombinants obtained in this study should be useful for further chromosome manipulation to introgress a small interstitial 5HL chromosome segment with the early heading gene(s) to wheat. Preferential occurrence of restricted types of recombinants is discussed in relation to homoeologous relationships between wheat and barley chromosomes.

Monophyletic origin of naked barley inferred from molecular analyses of a marker closely linked to the naked caryopsis gene (nud)

To elucidate the origin of naked barley, molecular variation of the marker sKT7 tightly linked to the nud locus was examined. A total of 259 (53 wild, 106 hulled domesticated, and 100 naked domesticated) barley accessions were studied. Restriction analysis of the sKT7 PCR-amplified product revealed the alleles I, II, III, and IV. All four alleles were found in wild barley, but allele IV was found only in a single accession from southwestern Iran. Hulled domesticated accessions showed alleles I, II, or III, but all naked domesticated accessions had allele IV. The distribution of allele IV in wild barley and its pervasive presence in naked domesticated lines support the conclusion that naked barley has a monophyletic origin, probably in southwestern Iran. The available results suggest two scenarios for the origin of naked barley: either directly from a wild barley with allele IV or from a hulled domesticated line with allele IV that later became extinct. Naked domesticated accessions from different regions of the world have extremely homogeneous DNA sequences at the sKT7 locus, supporting the monophyletic origin of naked barley. For allele IV, four haplotypes (IVb to IVe) were found in 30 naked accessions: IVb was predominant (66.7%) and widely distributed, while the other three haplotypes, differing by only one nucleotide at different positions relative to IVb, showed a localized distribution. The geographical distribution of the haplotypes of sKT7 allele IV suggests migration routes of naked domesticated barley in central and eastern Asia.

Interaction between two auxin-resistant mutants and their effects on lateral root formation in rice (Oryza sativa L.)

Since root elongation is very sensitive to auxin, screening for reduced inhibition in root elongation has been an important method for the detection of auxin-resistant mutants. Two recessive auxin-resistant lines of rice (Oryza sativa L. ssp. indica cv. IR8), arm1 and arm2, have been isolated by screening for resistance to 2,4-dichlorophenoxyacetic acid (2,4-D). arm1 displays a variety of morphological defects including reduced lateral root formation, increased seminal root elongation, reduced root diameter, and impaired xylem development in roots, while the arm2 phenotype is almost similar to wild-type IR8 except for a slightly reduced lateral root formation, impaired xylem development in roots and an enhanced plant height. Although the growth of arm2 roots exhibited a resistance to 2,4-D, it was sensitive to 1-naphthaleneacetic acid (NAA) as the wild type. At the same time, the arm2 roots showed a reduced [14C]2,4-D uptake while uptake of [3H]NAA was normal, suggesting that the resistance to 2,4-D of arm2 roots is due to a defect in 2,4-D uptake. To investigate the possible interaction between arm1 and arm2 genes, a double mutant has been constructed. The roots of arm1 arm2 double mutant were more resistant to 2,4-D and formed fewer lateral roots than those of either single mutant, suggesting that the two genes show synergistic effects with respect to both auxin response and lateral root formation. By contrast, all these mutants displayed the normal gravitropic response in roots, as did the wild-type plants. Taken together, Arm1 and Arm2 genes seem to function in different processes in the auxin-response pathways leading to lateral root formation.

Efficient fine mapping of the naked caryopsis gene ( nud) by HEGS (High Efficiency Genome Scanning)/AFLP in barley

The hulled or naked caryopsis character of barley ( Hordeum vulgare L.) is an important trait for edibility and to follow its domestication process. A single recessive gene, nud, controls the naked caryopsis character, and is located on the long arm of chromosome 7H. To develop a fine map around the nud locus efficiently, the HEGS (High Efficiency Genome Scanning) electrophoresis system was combined with amplified fragment length polymorphism (AFLP). From bulked segregant analysis of 1,894 primer combinations, 12 AFLP fragments were selected as linked markers. For mapping, an F(2 )population of 151 individuals derived from a cross between Kobinkatagi (naked type) and Triumph (hulled type) was used. Seven AFLP markers were localized near the nud region. A fine map was developed with one-order higher resolution than before, along with the seven anchor markers. Among the seven linked AFLP markers (KT1-7), KT1, KT2 and KT6 were co-dominant, and the former two were detected for their single-nucleotide polymorphisms (SNPs) in the same length of fragments after electrophoresis with the non-denaturing gels of HEGS. The nud locus has co-segregated with KT3 and KT7, and was flanked by KT2 and KT4, at the 0.3-cM proximal and the 1.2-cM distal side, respectively. Four of these AFLP markers were converted into sequence-characterized amplified region (SCAR) markers, one of which was a dominant marker co-segregating with the nud gene.

Differential effects of cultivated and wild barley 5H chromosomes on heading characters in wheat-barley chromosome addition lines

Wheat (Triticum aestivum L.)-barley (Hordeum vulgare L.) chromosome addition lines are possible vehicles for transferring barley genes into wheat. The barley 5H chromosome has genetic effects on the heading characters in wheat-barley addition lines: accelerating narrow-sense earliness, decreasing vernalization requirement and/or increasing photoperiodic sensitivity. To elucidate the effects of different 5H chromosomes under an identical wheat genetic background, two wheat-barley addition lines, i.e. cultivated barley 'New Golden' 5H chromosome added to 'Shinchunaga' wheat (Shi-NG5H) and wild barley H. vulgare ssp. spontaneum 5H chromosome added to 'Shinchunaga' wheat (Shi-Spn5H), were examined for their heading characters. The addition line Shi-NG5H showed a significantly lower vernalization requirement in comparison with 'Shinchunaga' wheat, whereas Shi-Spn5H did not. Furthermore, both NG5H and Spn5H chromosomes shortened narrow-sense earliness and increased photoperiodic sensitivity in wheat, but the effects of Spn5H were weaker than those of NG5H. The fact that NG5H and Spn5H showed differential effects on heading characters in wheat demonstrated that the heading characters were altered by the function of the barley genes located on 5H chromosomes, not merely by the aneuploid effect alone.

Molecular and physical mapping of a barley gene on chromosome arm 1 HL that causes sterility in hybrids with wheat

Addition of the long arm of barley chromosome 1H (1HL) to wheat causes severe meiotic abnormalities and complete sterility of the plants. To map the barley gene responsible for the 1H-induced sterility of wheat, a series of addition lines of translocated 1H chromosomes were developed from the crosses between the wheat 'Shinchunaga' and five reciprocal translocation lines derived from the barley line St.13559. Examination of the seed fertility of the addition lines revealed that the sterility gene is located in the interstitial 25% region of the 1HL arm. The genetic location of the sterility gene was also estimated by physically mapping sequence-tagged site (STS) markers and simple-sequence repeat (SSR) markers with known map locations. The sterility gene is designated Shw (sterility in hybrids with wheat). Comparison of the present physical map of 1HL with two previously published genetic maps revealed a paucity of markers in the proximal 30% region and non-random distribution of SSR markers. Two inconsistencies in marker order were found between the present physical map and the consensus genetic map of group 1 chromosomes of Triticeae. On the basis of the effects on meiosis and chromosomal location, the relationship of the present sterility gene with other fertility-related genes of Triticeae is discussed.

A DNA marker closely linked to the vrs1 locus (row-type gene) indicates multiple origins of six-rowed cultivated barley ( Hordeum vulgare L.)

The origin of six-rowed cultivated barley was studied using a DNA marker cMWG699 closely linked to the vrs1 locus. Restriction patterns of the PCR-amplified product of the cMWG699 locus were examined in 280 cultivated ( Hordeum vulgare ssp. vulgare) and 183 wild ( H. vulgare ssp. spontaneum) barleys. Nucleotide sequences of the PCR products were also examined in selected accessions. Six-rowed cultivated barleys were divided into two distinct groups, types I and II. Type I six-rowed cultivated barley was distributed widely while type II six-rowed cultivated barley was found only in the Mediterranean region. The type I sequence was also found in a wild barley accession from Turkmenistan whereas the type II sequence was also found in a two-rowed cultivated barley from North Africa and a wild barley from Morocco. These results suggested that the six-rowed type I and II barleys were derived from two-rowed type I and II barleys, respectively, by independent mutations at the vrs1 locus.

Physical locations of 5S and 18S-25S rDNA in Asian and American diploid Hordeum species with the I genome

The physical locations of 5S and 18S-25S rDNA sequences in 15 diploid Hordeum species with the I genome were examined by double-target in situ hybridization with pTa71 (18S-25S rDNA) and pTa794 (5S rDNA) clones as probes. All the three Asian species had a species-specific rDNA pattern. In 12 American species studied, eight different rDNA types were found. The type reported previously in H. chilense (the 'chilense' type) was observed in eight American species. The chilense type had double 5S rDNA sites - two sites on one chromosome arm separated by a short distance - and two pairs of major 18S-25S rDNA sites on two pairs of satellite chromosomes. The other seven types found in American species were similar to the chilense type and could be derived from the chilense type through deletion, reduction or addition of a rDNA site. Intraspecific polymorphisms were observed in three American species. The overall similarity in rDNA patterns among American species indicates the close relationships between North and South American species and their derivation from a single ancestral source. The differences in the distribution patterns of 5S and 18S-25S rDNA between Asian and American species suggest differentiation between the I genomes of Asian and American species. The 5S and 18S-25S rDNA sites are useful chromosome markers for delimiting Asian species, but have limited value as a taxonomic character in American species. On the basis of rDNA patterns, karyotype evolution and phylogeny of the I-genome diploid species are discussed.

Barley allele-specific amplicons useful for identifying wheat-barley recombinant chromosomes

Barley (Hordeum vulgare L.) is potentially a new source of genes for wheat (Triticum aestivum L.) improvement. Wheat-barley chromosome recombinant lines provide a means for introgressing barley genes to wheat genome by chromosome engineering, and since these are expected to occur only rarely in special cytogenetic stocks, an efficient selection skill is necessary to identify them. To convert RFLP markers to barley allele-specific PCR markers useful for effective production of wheat-barley recombinant lines, 91 primer sets derived from RFLP clones which were previously mapped to the barley chromosomes were examined for PCR amplification using 'Chinese Spring' wheat, 'Betzes' barley and the wheat-barley chromosome addition lines. The polymorphisms were detected by an agarose gel electrophoresis of the PCR products without digestion with restriction enzymes. Out of 81 primer sets producing polymorphisms between the wheat and barley genomes, 26 amplified barley chromosome-specific DNAs which were confirmed to be located on the same chromosome as the RFLP markers by using the wheat-barley chromosome addition lines. These amplified DNAs represent barley allele-specific amplicons, which distinguish barley alleles from their wheat homoeologous counterparts. The present investigation revealed a higher probability for obtaining allele-specific amplicons from genomic DNA-derived RFLP markers than from cDNA-derived ones. The barley allele-specific amplicons developed in this study, namely, four for chromosome 2H, two for 3H, seven for 4H, eight for 5H, one for 6H and four for 7H, are suitable for identifying 'Chinese Spring' wheat- 'Betzes' barley recombinant chromosomes. However, one out of eight barley allele-specific amplicons on chromosome 5H did not detect a unique barley band in a 'New Golden' barley chromosome 5H addition line of 'Shinchunaga' wheat, indicating there may be a need to reconstruct allele-specific amplicons with different barley cultivars.

Aluminum tolerance genes on the short arm of chromosome 3R are linked to organic acid release in triticale

Triticale, a hybrid between wheat and rye, shows a high degree of Al tolerance that is inherited from rye, but the mechanisms of high Al tolerance in both rye and triticale are unknown. We found that the short arm of chromosome 3R carries genes necessary for Al tolerance in triticale (x Triticosecale Wittmark cv Currency). Detailed comparative studies with a 3DS.3RL translocation line (ST22) and a non-substitution line (ST2) were conducted. Root elongation was similarly inhibited by Al in ST2 and ST22 during the first 12 h of Al treatment, but more strongly in ST22 than in ST2 at 18 h and thereafter. The root inhibition induced by other metals (Cu, Cd, and La) was similar between ST2 and ST22, suggesting that the action of the genes for Al tolerance on the short arm of triticale chromosome 3R is highly specific to Al. A 2-fold larger amount of malate and citrate was released from the roots of ST2 than from ST22 at 12 and 18 h after Al treatment, respectively. The marked lag phase in the inhibition of root elongation and the release of organic acids implies that the expression of genes on the short arm of triticale chromosome 3R is induced by Al, and that these genes are necessary for the release of organic acids.

The chromosomal distributions of Ty1-copia group retrotransposable elements in higher plants and their implications for genome evolution

Retrotransposons make up a major fraction--sometimes more than 40%--of all plant genomes investigated so far. We have isolated the reverse transcriptase domains of the Ty1-copia group elements from several species, ranging in genome size from some 100 Mbp to 23,000 Mbp, and determined the distribution patterns of these retrotransposons on metaphase chromosomes and within interphase nuclei by DNA:DNA in situ hybridization. With some exceptions, the reverse transcriptase domains were distributed over the length of the chromosomes. Exclusion from rDNA sites and some centromeres (e.g., slash pine, 23,000 Mbp, or barley, 5500 Mbp) is frequent, whereas many species exclude retrotransposons from other sites of heterochromatin (e.g., intercalary and centromeric sites in broad bean). In contrast, in the plant Arabidopsis thaliana, widely used for plant molecular genetic studies because of its small genome (c. 100 Mbp), the Ty1-copia group reverse transcriptase gene domains are concentrated in the centromeric regions, colocalizing with the 180 bp satellite sequence pAL1. Unlike the pAL1 sequence, however, the Ty1-copia signal is also detectable as weaker, diffuse hybridization along the lengths of the chromosomes. Possible mechanisms for evolution of the contrasting distributions are discussed. Understanding the physical distribution of retrotransposons and comparisons of the distribution between species is critical to understanding their evolution and the significance for generation of the new patterns of variability and in speciation.

In vitro phosphorylation of bovine cardiac muscle high molecular weight calmodulin binding protein by cyclic AMP-dependent protein kinase and dephosphorylation by calmodulin-dependent phosphatase

High molecular weight calmodulin binding protein (HMWCaMBP) is one of the major proteins expressed in bovine cardiac muscle. In this study, we report the phosphorylation and dephosphorylation of HMWCaMBP in vitro with a view to understand the function of this protein. The HMWCaMBP was phosphorylated by cAMP-dependent protein kinase with the incorporation of 2.30 mol of phosphate/mol of protein in the presence of EGTA. When phosphorylation was carried out in the presence of Ca2+/calmodulin (CaM), the incorporation of phosphate was reduced to 1.40 mol of phosphate/mol of protein. The decrease in the stoichometry of phosphorylation by Ca2+/CaM appears to be substrate directed i.e. due to the interaction of Ca2+/CaM with HMWCaMBP. The phosphorylated HMWCaMBP was unable to compete for free CaM in a CaM-dependent cyclic nucleotide phosphodiesterase (CaMPDE) assay. These results suggest that the phosphorylation sites may reside in or in proximity to the CaM-binding domain on HMWCaMBP since phosphorylated HMWCaMBP did not inhibit CaMPDE activity. HMWCaMBP was dephosphorylated by CaM-dependent phosphatase, calcineurin.

C-banding analysis on wild Emmer (Triticum dicoccoides Körn) strains with and without spontaneous reciprocal translocations

C-banding polymorphism was analyzed in eight strains of wild Emmer, Triticum dicoccoides Körn, which included six translocation homozygotes reported previously. Polymorphisms were detected in all of the strains examined, and the breakpoints of five spontaneous translocations were successfully identified by C-bands. Of the eight breakpoints that could be precisely identified, one was located in the centromeric region while the remaining seven were located in proximal to distal euchromatic regions. The two breakpoints of one translocation could only be approximately localized to proximal regions due to the scarcity of C-bands. The present results are in contrast with those observed on T. araraticum, another wild tetraploid wheat belonging to the Timopheevi group, in which most of the breakpoints were located in centromeric regions. In T. dicoccoides, the six translocation chromosome types were derived from the standard karyotype primarily by a mechanism other than centric breakage-fusion.

High crossability of wild barley (Hordeum spontaneum C. Koch) with bread wheat and the differential elimination of barley chromosomes in the hybrids

Four bread wheat (Triticum aestivum L.) cultivars, 'Aobakomugi', 'Chinese Spring', 'Norin 61' and 'Shinchunaga', were pollinated with five barley lines/cultivars consisting of three cultivated barley (Hordeum vulgare L.) lines, 'Betzes', 'Kinai 5' and OHL089, and two wild barley (Hordeum spontaneum C. Koch) lines, OUH602 and OUH324. Crossability, expressed as the percentage of embryo formation, varied from 0 to 55.4% among the cross combinations. The two wild barley lines generally had a higher crossability than the previously reported best pollinator, 'Betzes', and some Japanese wheat cultivars were better as the female parent than 'Chinese Spring'. Ninety four hybrid plants were obtained from 250 embryos cultured, and their somatic chromosome numbers ranged from 21 to 36. Eighteen plants were mosaic in chromosome number. Twenty one-chromosome plants appeared most frequently (45.7%) followed by 28-chromosome plants (14.9%). C-banding analysis revealed that elimination of barley chromosomes was mainly responsible for the occurrence of aneuploid plants. In hypoploids derived from 'Betzes'-crosses, chromosome 5 was preferentially eliminated as previously reported, while in hypoploids derived from OUH602-crosses, chromosome 4 was preferentially eliminated. The wild barley line OUH602 may be a useful parent for producing a new wheat-barley addition set because of its high crossability with wheat and a different pattern of chromosome elimination.

High molecular weight calmodulin-binding protein is phosphorylated by calmodulin-dependent protein kinase VI from bovine cardiac muscle

A high molecular weight calmodulin-binding protein (HMW CaMBP) from bovine heart cytosolic fraction was purified to apparent homogeneity. A novel CaM-dependent protein kinase was originally discovered when the total CaM-binding protein fraction from cardiac muscle was loaded on a gel filtration column. The CaM-dependent protein kinase was shown by gel filtration chromatography to have an apparent molecular mass of 36,000 daltons. The CaM-dependent protein kinase has been highly purified by sequential chromatography on DEAE-Sepharose Cl 6B (to remove calmodulin), CaM-Sepharose 4B, phosphocellulose, Sepharose 6B gel filtration and Mono S column chromatographies. The highly purified protein kinase stoichiometrically phosphorylated the HMW CaMBP in a Ca2+/CaM-dependent manner. The phosphorylation resulted in the maximal incorporation of 1 mol of phosphate/mol of the HMW CaMBP. The distinct substrate specificity of this protein kinase indicates that it is not related to the known protein kinases (I, II, III, IV and V) that have been already characterized, therefore we would like to designate this novel kinase as a CaM-dependent protein kinase VI.