Comparative analysis of S haplotypes with very similar SLG alleles in Brassica rapa and Brassica oleracea

Self-incompatibility in Brassica is controlled by a single multi-allelic locus (the S locus) which harbors at least two highly polymorphic genes, SLG and SRK. SRK is a putative transmembrane receptor kinase and its amino acid sequence of the extracellular domain of SRK (the S domain) exhibits high homology to that of SLG. The amino acid sequences of the SLGs of S8 and S46 haplotypes of B. rapa are very similar and those of S23 and S29 haplotypes of B. oleracea were also found to be almost identical. In both cases, SLG and the S domain of SRK of the same haplotype were less similar. This seems to contradict the idea that SLG and SRK of the same haplotype have the same self-recognition specificity. In the transmembrane-kinase domain, the SRK alleles of the S8 and S46 haplotypes had almost identical nucleotide sequences in spite of their lower homology in the S domain. Such a cluster of nucleotide substitutions is probably due to recombination or related events, although recombination in the S locus is thought to be suppressed. Based on our observations, the recognition mechanism and the evolution of self-incompatibility in Brassica are discussed.

Myophosphorylase deficiency and limb-girdle muscular dystrophy in the same pedigree

We report 2 familial patients with limb-girdle muscular dystrophy (LGD). The parents of patient 1 showed a consanguineous marriage and patient 2 was a paternal cousin of patient 1. Slowly progressive muscular weakness/wasting and dystrophic changes in the biopsied muscles were observed in both patients. However, a quantitative assay revealed a severely reduced myophosphorylase activity in patient 1 with normal activity in patient 2. A semi-ischemic exercise test disclosed no elevation of venous lactate in patient 1 with a normal increase in patient 2. A leukocytes DNA analysis in patient 1 did not show the gene deficits previously recognized in patients with McArdle's disease (McD). Patient 1 may only have abnormal myophosphorylase activity with dystrophic changes secondary to the myophosphorylase deficiency or coincidentally two genomic abnormalities for McD and LGD. LGD still has heterogenous etiologies and the responsible genes for these two disorders may be closely mapped.

Intrarenal and subcellular localization of rat CLC5

Dent's disease, an inherited disorder characterized by hypercalciuria, nephrolithiasis, nephrocalcinosis, rickets, low-molecular-weight proteinuria, Fanconi's syndrome, and renal failure, is caused by mutations in the renal chloride channel, CLC5. The normal role of CLC5 is unknown. We have investigated the intrarenal and subcellular localization of CLC5 in rat kidney by in situ hybridization and immunohistochemistry. By in situ hybridization, CLC5 mRNA was detected predominantly in cortical medullary ray and outer medullary tubule epithelial cells. Polyclonal antiserum was generated against a CLC5 fusion protein, affinity purified, and immunoadsorbed against CLC3 and CLC4 to yield a CLC5 isoform-specific antiserum. By immunohistochemistry, CLC5 protein was localized to the intracellular domain of tubular epithelial cells in the S3 segment of the proximal tubule and the medullary thick ascending limb. By subcellular membrane fractionation and flow cytometry, CLC5 expression was found in outer medullary endosomes. These findings are consistent with a model in which CLC5 encodes an endosomal chloride channel that facilitates acidification and trafficking of renal epithelial endosomes.

A comparison of prosthetic materials used to repair abdominal wall defects

Large abdominal wall defects may require a prosthesis for closure. The aim of our study was to identify the best material for abdominoplasty in pediatric patients. One hundred twenty-eight Wistar KY strain male rats (3 weeks old) were used. All animals underwent celiotomy via a midline skin incision. They were divided into seven groups as follows: the animals in groups 1 through 6 underwent full-thickness abdominal wall excision 3 cm in diameter. The animals in group 1 underwent primary closure. In groups 2 through 6 the defect was closed with prosthetic material. In Group 7, a sham operation was performed. Daily weights were measured. The animals were killed after 3 and 9 weeks. Adhesion scores were assigned for each group. Vicryl mesh resulted in the fewest adhesions and had no effect on weight gain in the developing rats.

Molecular characterization and tissue distribution of a new organic anion transporter subtype (oatp3) that transports thyroid hormones and taurocholate and comparison with oatp2

Two complementary DNAs for the organic anion transporter subtypes oatp2 and oatp3, which transport thyroid hormones as well as taurocholate, were isolated from a rat retina cDNA library. The sequence of oatp2 is identical to that recently reported (Noé, B., Hagenbuch, B., Stieger, B., and Meier, P. J. (1997) Proc. Natl. Acad. Sci. U. S. A. 94, 10346-10350), whereas the sequence of oatp3 is novel. oatp3 consists of 670 amino acid residues and exhibits a structural architecture common to the organic anion transporter family, possessing the 12 putative membrane-spanning segments. Oocytes injected with oatp2 and oatp3 cRNAs showed taurocholate uptake in a saturable manner. The oatp2 and oatp3 cRNA-injected oocytes also showed significant uptake of both thyroxine and triiodothyronine. Northern blot and in situ analyses showed that the oatp2 mRNA was widely expressed in neuronal cells of the central nervous system, especially in the hippocampus, cerebellum, and choroid plexus as well as in the retina and liver. The oatp3 mRNA was highly expressed in the kidney and moderately abundant in the retina. This suggests that oatp2 and oatp3 are multifunctional transporters involved in the transport of thyroid hormones in the brain, retina, liver, and kidney.

Medial nigral dopamine neurons have rich neurotrophin support in humans

To assess the action of neurotrophin in human dopaminergic neurons, we studied the immunolocalization of neurotrophins or trks in human substantia nigra pars compacta (SNc). The neuromelanin-containing neurons in the SNc showed immunoreactivities for neurotrophins or trks, suggesting an autocrine/paracrine regulation. Quantitative analysis revealed that the percentage of those expressing NGF-like immunoreactivity (NGF-LI), BDNF-LI, NT3-LI, trkA-LI, trkB-LI, or trkC-LI was 66%, 74%, 85%, 66%, 71% or 86%, respectively. The percentage of cells expressing neurotrophins or trks was higher in the medial part than in the lateral part of the SNc. The preferential expression of neurotrophin-trk systems in the medial neurons may, at least partially, explain the differential susceptibility in Parkinson's disease.

Immunohistochemical and ultrastructural characterization of ubiquitinated eosinophilic fibrillary neuronal inclusions in sporadic amyotrophic lateral sclerosis

We found eosinophilic fibrillary neuronal inclusions (EFNI) that were argyrophilic and immunoreactive for anti-ubiquitin in the cerebral cortex of a patient with sporadic amyotrophic lateral sclerosis (ALS) and mild personality changes. Both hematoxylin and eosin and Bodian's preparations revealed the EFNI to be rod-, flame-shaped, or spherical structures existing within the swollen neuronal perinuclear region in the third, fifth, and sixth layers of the fronto-parieto-temporal cortices including the primary motor cortex. On electron microscopy, filamentous profiles aggregated and formed a single bundle or globule in the neuronal perikaryon without any limiting membrane. Most EFNI had a characteristic multiple layer arrangement. The inner core consisted of randomly oriented granule-free tubules with a fuzzy outer contour, measuring 15-20 nm in diameter. The surrounding layer was made up of granule-associated filaments, electrondense free granules, and small vesicular profiles. Large autolysosome-like membrane-bound vesicular profiles were found scattered at the periphery. Neurofilaments were usually mingled with in the surrounding cytoplasm. Many EFNI were also found in dendrites, but only a few in axons. Both granule-free tubules and granule-associated filaments expressed ubiquitin protein epitopes. Aberrant phosphorylation of neurofilament protein and induction of alphaB-crystallin were shown to exist in EFNI-bearing swollen neurons. Despite having a variety of histological appearances, our observations revealed that EFNI all have common immunocytochemical and ultrastructural characteristics, and thus we assume that EFNI represent a series of cytological alterations in the motor and extra-motor cortices of ALS patients.

[Transferability of tazobactam/piperacillin (TAZ/PIPC) to cerebrospinal fluid of rabbit with meningitis caused by Staphylococcus aureus]

The transferability of tazobactam/piperacillin (TAZ/PIPC) to cerebrospinal fluid (CSF) was studied employing rabbits with experimental meningitis caused by Staphylococcus aureus. 125 or 250 mg/kg of TAZ/PIPC was intravenously administered to rabbits with experimental meningitis then concentrations of TAZ and PIPC in CSF and serum were measured. In the group to which 125 mg/kg of TAZ/PIPC was administered, mean concentration of TAZ in CSF was 7.3 and 2.4 micrograms/ml at 30 and 60 min after administration, respectively, and concerning PIPC, it was 10.1 and 3.5 micrograms/ml, respectively. CSF/serum ratio of TAZ was 29.4% and 31.4%, respectively, and that of PIPC was 24.3 and 35.6%, respectively. In the group to which 250 mg/kg of TAZ/PIPC was administered, mean concentration of TAZ in CSF was 16.5 and 12.6% micrograms/ml, respectively, and concerning PIPC, it was 25.6 and 18.2 micrograms/ml, respectively. CSF/serum ratio of TAZ was 22.1 and 56.1%, respectively, and that of PIPC was 12.2 and 51.9%, respectively. Addition of TAZ did not make significant change of transferability of PIPC to CSF. Considering the antibacterial effect of TAZ/PIPC against main causative organism of meningitis, this agent was thought to be effective for the treatment of purulent meningitis.

Neutrophin switching in spinal motoneurons of amyotrophic lateral sclerosis

To clarify the roles of neurotrophins in the human spinal motoneurons, with special reference to amyotrophic lateral sclerosis (ALS), we studied the immunohistochemical localizations of neurotrophins and their receptors in spinal cords of patients with ALS and compared them with controls. In the controls, the majority of motoneurons showed BDNF-, NT3-, trkB- and trkC-like immunoreactivity (-LI) suggesting that the motoneurons receive an autocrine regulation by both BDNF and NT3. In ALS patients, about three-quarters of the motoneurons had degenerated and the remaining motoneurons showed significantly decreased BDNF-LI, increased NGF- and trkA-LI. These findings indicated neurotrophin-switching in the remaining spinal motoneurons of ALS patients from BDNF and NT3 responsive to NGF responsive.

Polymorphism of the S-locus glycoprotein gene (SLG) and the S-locus related gene (SLR1) in Raphanus sativus L. and self-incompatible ornamental plants in the Brassicaceae

The S-locus glycoprotein gene, SLG, which participates in the pollen-stigma interaction of self-incompatibility, and its unlinked homologue, SLR1, were analyzed in Raphanus sativus and three self-incompatible ornamental plants in the Brassicaceae. Among twenty-nine inbred lines of R. sativus, eighteen S haplotypes were identified on the basis of DNA polymorphisms detected by genomic Southern analysis using Brassica SLG probes. DNA fragments of SLG alleles specifically amplified from eight S haplotypes by PCR with class I SLG-specific primers showed different profiles following polyacrylamide gel electrophoresis, after digestion with a restriction endonuclease. The nucleotide sequences of the DNA fragments of these eight R. sativus SLG alleles were determined. Degrees of similarity of the nucleotide sequences to a Brassica SLG (S6SLG) ranged from 85.6% to 91.9%. Amino acid sequences deduced from these had the twelve conserved cysteine residues and the three hypervariable regions characteristic of Brassica SLGs. Phylogenetic analysis of the SLG sequences from Raphanus and Brassica revealed that the Raphanus SLGs did not form an independent cluster, but were dispersed in the tree, clustering together with Brassica SLGs. These results suggest that diversification of the SLG alleles of Raphanus and Brassica occurred before differentiation of these genera. Although SLR1 sequences from Orychophragmus violaceus were shown to be relatively closely related to Brassica and Raphanus SLR1 sequences, DNA fragments that are highly homologous to the Brassica SLG were not detected in this species. Two other ornamental plants in the Brassicaceae, which are related more distantly to Brassica than Orychophragmus, also lacked sequences highly homologous to Brassica SLG genes. The evolution of self-incompatibility in the Brassicaceae is discussed.

Monte Carlo studies on potentiometric titration of poly(glutamic acid)

The potentiometric titration of poly(glutamic acid) with special attention to its helix-coil transition is investigated in terms of the previously developed Monte Carlo method. The simulations of the potentiometric titration are carried out for helical and coiled form of the peptide, separately. A cylindrical rod with spherical ionizable groups is adopted as each conformational model of poly(glutamic acid) molecule. A spherical charge with a hard core potential is assumed as a mobile hydrated ion. The helix-coil transition curves are analyzed by the Zimm-Bragg theory. A satisfactory agreement is achieved for the titration curves with the experimental data in most cases. The significance and the limitations of the simulation method are discussed.

[Toremifene sensitized the effect of adriamycin on human breast cancer cell lines]

A experimental study was reported here to clarify the chemosensitizing effect of Toremifene (Tor) on human breast cancer cell lines. MCF7, estrogen dependent adriamycin (ADM) resistant cell, and MDA-MB231, estrogen independent cell, were preincubated for 8 hours with Tor 0, 4 or 10 microM, then with ADM 0-10 micrograms/ml for one hour. After that, cells were cultured for 24 hours, and their cell cycle and growth were analyzed with flow-cytometry and MTT assay, respectively. Furthermore, the ADM concentrations of these cells were measured by high-performance liquid chromatographic assay (HPLC). Although flowcytometric analysis showed the enhancement of Gz block only in MCF7 at the ADM concentration with 5 micrograms/ml, the sensitizing effect was revealed by MTT assay, and the elevation of ADM concentration was found in HPLC assay in both cells. The chemosensitizing effect of Toremifene was observed in estrogen dependent and independent cell lines.

[Analysis for predicting the prognostic factors of gastrointestinal tract leiomyosarcoma using MIB-1 and DNA flow cytometry]

PURPOSE

The present study was undertaken to investigate the possibility of determining a prognosis for gastrointestinal tract leiomyosarcoma with the use of DNA analysis and MIB-1 staining.

SUBJECTS AND METHODS

Malignant tumors originating in smooth muscle of the gastrointestinal tract, surgically excised from 23 lesions in 17 patients (stomach; 8 cases, 12 lesions; small intestine: 6 cases, 8 lesions; colon: 3 cases, 3 lesions) and embedded in paraffin, were examined. DNA was analyzed using flow cytometry to produce a DNA histogram, and aneuploidy and diploidy were found. MIB-1 staining was done in conformity with the ABC method.

RESULTS

1. An investigation of prognoses using the Kaplan-Meier method revealed a tendency for more favorable prognoses in patients determined to be aneuploid through DNA analysis. However, this was not significantly better than those exhibiting diploidy. 2. All patients who died had a MIB-1 staining positivity rate of over 10%, while all patients who had no recurrence within one year or survived had a MIB-1 staining positivity of less than 10%. 3. No consistent trends were observed between MIB-1 positivity rate and DNA analysis, MIB-1 positivity rate and size of tumor, or DNA analysis and size of tumor. 4. The MIB-1 positivity rate of patients with remote metastases was significantly greater than that of patients with no remote metastases.

CONCLUSION

From the fact that patients with MIB-1 positivity rates of greater than 10% had a poor prognosis, while those with rates of less than 10% had a favorable prognosis, we conclude that a MIB-1 positivity rate of 10% is an important value in determining the prognosis of patients with gastrointestinal tract leiomyosarcomas.

Repeated injections of nicergoline increase the nerve growth factor level in the aged rat brain

We studied whether nicergoline, clinically active in chronic cerebrovascular insufficiency, influences nerve growth factor (NGF) levels in the rat brain. In young Fischer rats, repeated intraperitoneal injections of nicergoline (0.3 and 1.0 mg/kg body weight) did not show any effects on frontal NGF contents determined by a highly sensitive enzyme immunoassay. In aged rats, 22-month-old, however, repeated injections of nicergoline (1.0 mg/kg body weight) induced a significant increase in the NGF level in the frontal region.

CAG repeat length and disease duration in Machado-Joseph disease: a new clinical classification

To evaluate the clinical characteristics of Machado-Joseph disease (MJD) with reference to CAG repeat length and disease duration, we analyzed neurologic findings in 108 patients from 84 families. The majority of MJD patients presented with an ataxic gait as the initial symptom. Dysarthria and nystagmus were observed from an early stage. Bulging eyes, muscle atrophy and bradykinesia developed later. Patients with a shorter CAG repeat length or later onset had more frequent involvement of proprioceptive sensory deficit. Incidence of abnormal reflexes, tones, and proprioceptive sensation was not associated with disease duration, but with CAG repeat length. Based on these results, we propose a new clinical classification: type A (juvenile type), with hyperreflexia and dystonia, but without a proprioceptive sensory deficit; type C (adult type), with hyporeflexia and a proprioceptive sensory deficit, but without dystonia; and type B (intermediate type), the remaining patients with a mixed presentation.

[Efficacy and safety of sulbactam/cefoperazone for hepato-biliary infections]

We studied efficacy and safety of sulbactam/cefoperazone (SBT/CPT) in the treatment of biliary tract infections in hospitalized patients at 26 hospitals from February 1993 to March 1995. Secondary to dropout, 273 out of 338 patients entered in the study were evaluated, 127 patients with cholecystitis, 132 patients with cholangitis, and 14 patients with liver abscesses. Of these, 93 patients (34.1% had malignancy as an underlying disease. SBT/CPZ had an efficacy of 79.9% (218 patients; excellent: 52, good: 166), with the efficacy in patients with cholecystitis, cholangitis and liver abscess at 89.0% (113 patients), 77.3% (102 patients and 21.4% (3 patients), respectively. A significant difference (p < 0.05) was observed in the efficacy rates of patients with (59 patients [63.4%]) and without malignancy (159 patients [88.3%]). A total of 84 strains were isolated from bile specimens of 53 patients, and the major isolates were Escherichia coli, Pseudomonas aeruginosa and Enterococcus spp. Two or more bacterial strains were isolated simultaneously in 20 patients. Mild or moderate side effect (allergic reaction including rash etc.) were noted in 4 patients (1.18%), and laboratory abnormalities (increased GOT, etc.) were in 16 patients (4.71%) out of the total 338 patients. This study clearly demonstrated that SBT/CPZ retains its excellent clinical efficacy and safety profile, throughout its use over the past decade.

Substrate recognition by mitochondrial processing peptidase toward the malate dehydrogenase precursor

Mitochondrial processing peptidase (MPP) cleaves the extension peptides of precursor proteins newly imported into the mitochondria. Using synthetic oligopeptides modeled on the extension peptide of malate dehydrogenase, the critical elements of the substrate for the processing of MPP were determined [Niidome, T., Kitada, S., Shimokata, K., Ogishima, T., and Ito, A. (1994) J. Biol. Chem. 269, 24719-24722; Ogishima, T., Niidome, T., Shimokata, K., Kitada, S., and Ito, A. (1995) ibid. 270, 30322-30326]. In the present study, we constructed mutant precursors and compared the processing reaction with that of the peptide substrates to confirm the validity of use of peptide substrates. In both cases, the arginine residue presents at a proximal (-2) position relative to the processing site proved to be important for the processing. The distal arginine residue at position 7 was replaceable with alanine with no significant loss in cleavage efficiency if the precursor protein contained two consecutive arginine residues at a proximal position, although the arginine residue at a position 7 was indispensable in the model peptide. The proline residue, lying between the distal and proximal arginine residues, which is assumed to break a continuous alpha-helix region in the extension peptide, was needed for the processing. This peptidase has a preference for aromatic amino acids at the P1' site. These results were essentially the same as those obtained with model peptides except for the role of the distal arginine. We also found that amino acids at P2' and P3' sites had some effects on the processing. Thus we concluded that an effective combination of model peptides with precursor proteins is needed for the studies on MPP responsible substrate-recognition mechanisms.

[A case of spastic tetraplegia with medullo-cervical atrophy]

A 48-year-old man, who had spastic tetraplegia and a marked atrophy of the medulla oblongata and upper cervical cord, was reported. He began to walk in spastic fashion at the age of 12 years, and was diagnosed as spastic paraplegia. His father, whose onset of the disorder was 35 years old and died of pneumonia at the age of 69 years, manifested symptoms and a course, both resembling those of the present patient. Generalized weakness progressed gradually, and the patient was confined to bed in his forties. On admission, he showed markedly increased tendon reflexes and pathological reflexes in all the extremities. Muscular weakness was severe in the neck, trunk and extremities, and mild in the facial muscles. There were neither bulbar sign, significant respiratory failure nor fasciculation of muscles. A needle EMG examination revealed no apparent neuropathic findings. MR imaging showed a marked atrophy of the medulla oblongata and upper cervical cord, which was not considered to be secondary to vascular or infectious diseases. Though sensory evoked potentials showed no response at the latencies of central nervous components, visual evoked potentials, brainstem auditory evoked response and blink reflex were normal. This case might represent an unknown hereditary degenerative disease with autosomal dominant inheritance.

Anti-platelet aggregation activity of some pyrazines

This report describes the anti-platelet aggregation activity of 48 pyrazines. Among alkyl- and arylpyrazines tested, 2,3-diphenylpyrazines showed the strongest anti-platelet aggregation activity. Then, various substituents were introduced into the phenyl groups, and the 2,3-bis(p-methoxyphenyl)pyrazine derivatives were consequently found to possess considerably strong inhibitory activity.

[Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy--report of an autopsied Japanese case]

We report a 75-year old Japanese man with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). His family had no consanguinous marriage and his grandfather had migraine attacks. His father showed uncontrollable emotion at the age of 59 followed by gait disturbance, disorientation, pseudobulbar palsy and died at the age of 63. The patient had migraine attacks with aura since 10 year-old and showed uncontrolableness of his emotion and gait disturbance at the age of 63 followed by disorientation, urinary incontinence and pseudobulbar palsy, and died from aspiration pneumonia at the age of 75. The postmortem examination revealed an arteriopathy in the cerebral white matter and meningeal vessels and multiple infarctions in the cerebral white matter corpus callosum, basal ganglia, middle cerebellar peduncle and pontine tegmentum. The affected arterial walls showed eosinophilic and periodic acid Schiff (PAS)-positive granules in the media, which were composed of numerous electron dense small granules in varying sizes on electron microscopic examinations. These granules showed complements (Clq, C3, C4)-like immunoreactivity but did not have IgG-, IgM-, IgA-, kappa and lambda chain-, or beta-amyloid-like immunoreactivities. The clinicopathological features in this patient were compatible with those reported as CADASIL in the European countries and this is the first case report of CADASIL in Japanese race.

Two cases of MND/ALS developing the syndrome of inappropriate secretion of antidiuretic hormone

We report 2 autopsy-proven cases of motor neuron disease/amyotrophic lateral sclerosis (MND/ALS), who developed the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) prior to the respiratory failure. With respect to the underlying mechanisms of SIADH in the cases, we considered two factors; 1) dysfunction of the feedback system in ADH secretion via intrathoracic volume receptors caused by changes in intrathoracic circulation, and 2) primarily functional abnormalities in the limbic system which could influence hypothalamic osmoreceptors. It appears that SIADH can be followed by an exacerbation of respiratory dysfunction in MND/ALS.

Chronic expanding hematoma in the chest

We herein report the successful surgical treatment of 2 cases of chronic expanding hematoma in the chest. The first patient, who had undergone thoracoplasty 42 years earlier due to tuberculosis, became aware of a slowly growing mass protruding in the lateral thoracic wall. The second patient, who had tuberculous pleurisy 36 years earlier, was referred to our department because of a slowly expanding intrathoracic mass revealed by a roentgenogram. The tumors, which were encapsulated chronic hematomas, were both surgically resected. These cases are rare because of the development of a very large mass after undergoing treatment for tuberculosis more than 30 years previously.

Molecular features of the CAG repeats of spinocerebellar ataxia 6 (SCA6)

Spinocerebellar ataxia 6 (SCA6) is an autosomal dominant spinocerebellar degeneration caused by the expansion of the polymorphic CAG repeat in the human alpha1A voltage-dependent calcium channel subunit gene (CACNL1A4 gene). We have analyzed 60 SCA6 individuals from 39 independent SCA6 Japanese families and found that the CAG repeat length is inversely correlated with the age of onset (n = 58, r = -0.51, P < 0.0001). SCA6 chromosomes contained 21-30 repeat units, whereas normal chromosomes displayed 6-17 repeats. There was no overlap between the normal and affected CAG repeat number. The anticipation of the disease was observed clinically in all eight parent-child pairs that we examined; the mean age of onset was significantly lower (P = 0.0042) in children than in parents. However, a parent-child analysis showed the increase in the expansion of CAG repeats only in one pair and no diminution in any affected cases. This result suggests that factors other than CAG repeats may produce the clinical anticipation. A homozygotic case could not demonstrate an unequivocal gene dosage effect on the age of onset.

Striking sequence similarity in inter- and intra-specific comparisons of class I SLG alleles from Brassica oleracea and Brassica campestris: implications for the evolution and recognition mechanism

Self-incompatibility in Brassica is controlled by a single multi-allelic locus (S locus), which contains at least two highly polymorphic genes expressed in the stigma: an S glycoprotein gene (SLG) and an S receptor kinase gene (SRK). The putative ligand-binding domain of SRK exhibits high homology to the secretory protein SLG, and it is believed that SLG and SRK form an active receptor kinase complex with a self-pollen ligand, which leads to the rejection of self-pollen. Here, we report 31 novel SLG sequences of Brassica oleracea and Brassica campestris. Sequence comparisons of a large number of SLG alleles and SLG-related genes revealed the following points. (i) The striking sequence similarity observed in an inter-specific comparison (95.6% identity between SLG14 of B. oleracea and SLG25 of B. campestris in deduced amino acid sequence) suggests that SLG diversification predates speciation. (ii) A perfect match of the sequences in hypervariable regions, which are thought to determine S specificity in an intra-specific comparison (SLG8 and SLG46 of B. campestris) and the observation that the hypervariable regions of SLG and SRK of the same S haplotype were not necessarily highly similar suggests that SLG and SRK bind different sites of the pollen ligand and that they together determine S specificity. (iii) Comparison of the hypervariable regions of SLG alleles suggests that intragenic recombination, together with point mutations, has contributed to the generation of the high level of sequence variation in SLG alleles. Models for the evolution of SLG/SRK are presented.