The interactions between two groups of rice endophytic bacterial strains and several rice cultivars were investigated. Various strains of Rhizobium leguminosarum bv. trifolii, originally isolated from rice plants grown in Egypt, comprise one group. The second group of bacterial strains was isolated from rice cultivars grown in the Philippines. Inoculation experiments with rice seedlings showed that specific isolates of these rice-associating bacteria could either promote, inhibit, or have no influence on rice plant growth. Furthermore, these growth effects were greatly influenced by the environmental growth conditions used. Studies to examine root colonisation patterns, using Rhizobium strains into which a plasmid expressing the green fluorescent protein has been placed, showed that the bacteria preferentially colonise rice seedling surfaces mainly in clumps. This occurs along grooves on the rice root surface, or at the emerging lateral root zones and at the root tips. However, rhizobia could also colonise intercellularly in lateral roots formed on the main roots near the culm region of the seedling. Under the growth conditions used, this occurred most frequently with strain R4 which multiplied and migrated to form long lines of individual bacterial cells along the inside of growing lateral roots. A bioassay to measure bacterial multiplication in rice leaves showed that the rice-associating strains can multiply and survive at different rates within these tissues. They were not, however, detected migrating into other parts of the leaf from the original site of pressure-infiltration, indicating that the bacterial ability to migrate within the lateral roots is not matched by a similar capacity in rice leaves. We suggest that some of these rice-associating bacteria possess important genes that enhance their ability to intimately colonise niches on and within rice tissues, and promote rice plant growth.

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Thirty-four families with a child or fetus with Turner's syndrome were studied using a series of polymorphic DNA probes. Analysis of the origin of the normal X chromosome was possible in all cases. In 16 families with 45,X (four fetuses and 12 livebirths), the observed X was maternal in each case, indicating a preferential loss of the paternal sex chromosome at, or before, conception. In the remaining 18 families with a variety of karyotypes, but especially in those where the child had an isochromosome of Xq or a ring X, there was again a strong tendency for the normal X to be maternal. Analysis of parental ages was performed with known origin of each abnormality, but no evidence for an increased or decreased parental age effect was detected.Turner's syndrome is one of the most common chromosomal abnormalities with an estimated frequency at conception of 1-5%. Most affected fetuses are, however, spontaneously aborted and the residual birth frequency is 1 in 2500 to 5000 females.' In a large consecutive study the majority of fetuses were found to have monosomy X (45,X) with 45,X/46,XX in the remainder, whereas in the same study, among liveborn Turner's syndrome patients, 53% were 45,X, 14-8% were mosaic 45,X/46,XX, 90/o were 46,Xi(Xq)/ 45,X, 4 90/o were mosaic 47,XXX/45,X, and the remaining 9-7% showed five other karyotypes (46, 46, mosaic applicable to cultured cells from affected fetuses, were only informative in a proportion (31%) of families, and were biased in that informative families were more frequent for 45,Xm than for 45,XP.3 4 The development of multiple polymorphic DNA markers for the X chromosome offers an alternative approach which should avoid these difficulties. Hassold et a15 6 used this alternative approach to study 40 families with Turner's syndrome where the majority were spontaneously aborted fetuses, and were able to identify the parental origin in 35 (88%) of their families. We describe our results from a study of 34 families in which the majority were live born and where the origin of the abnormality has been determined for a variety of karyotypic abnormalities. Patients and methods ASCERTAINMENT OF CASESFamilies for this study were recruited from the records of the West of Scotland Regional Genetics Service and with the assistance ofthe United Kingdom Child Growth Foundation. CYTOGENETIC ANALYSISChromosomal analysis was undertaken using standard cytogenetic techniques on peripheral blood lymphocytes or cultured products of conception. Two families where the proband had Turner's syndrome but 45,X/46,XY (that is, a paternal defect) were excluded from DNA analysis.DNA ANALYSIS DNA was extracted from cultured fetal cells in the case of an affected fetus or from peripheral blood lymphocytes of affected children and of both parents.DNA samples were digested with the appropriate restriction enzymes under the conditions specified by the manufacturers. The resulting fragments were fractionated on 0-8% agarose gels and Southern blotted onto Hybond-N (Amersham) followed by hybridisation wi...

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New plant bioassays have been developed to (a) study root morphogenesis in small seeded legumes, and (b) enable the routine examination of large numbers of independently transformed plants. In addition, these bioassays enable analysis of specific plant gene expression. The single leaf plantlet assay uses simplified plants that are without shoot meristems, have a photosynthetic organ, grow roots which can be nodulated by Rhizobium bacteria, and can form lateral roots. The rooted cotyledon assay (RCA) was developed to investigate root morphogenesis of clover plants. Studies showed that early in the development of the root there was a cotyledon-derived inhibitor that could inhibit the continued growth of Rhizobium-induced nodule primordia. However, the activity of this inhibitor diminished with continued growth and maturation of the root. Rhizobia that can synthesise wild-type Nod factors can partially overcome this inhibition of nodule formation, the Nod signals acting as 'anti-cotyledon inhibitors'. Comparison of the RCA plantlets with normal seedlings suggests that the rooted cotyledons have a slightly slower root maturation, which enables the experimentalist time to probe mechanisms underlying root development. The rooted leaf assay was developed so that the symbiotic and physiological properties of large numbers of transgenic plants could be studied. This is a rapid technique that can use either untransformed or recently transformed plant material, and avoids the potential problem of a disturbed hormone balance that is inherent in the use of 'hairy roots' generated by the use of the Agrobacterium rhizogenes-mediated transformation of small-seeded legumes.