Requisite Morphologic Interaction for Attachment between Ulva pertusa (Chlorophyta) and Symbiotic Bacteria

In order to understand the morphogenesis-inducing mechanism of Ulva pertusa by symbiotic bacteria, we observed the requisite conditions of bacteria for attachment to U. pertusa for algal morphogenesis. Non-morphogenesis-inducing bacterial mutants derived by ultraviolet irradiation did not attach onto the surface of this alga. Scanning electron microscopic observation during the process of morphogenesis in U. pertusa revealed a network-like structure formed on the algal surface within 1 week after application of bacteria. The bacteria attached onto the alga after 2 weeks of incubation. After this attachment process the morphologic change was observed in U. pertusa. Received August 7, 1997; accepted July 24, 1998.     

Cloning and Sequencing of a 23-kb Region of the Bacillus subtilis Genome between the iol and hut Operons

Within the framework of an international project for the sequencingof the entire Bacillus subtilis genome, a 23-kb chromosomalsegment, which covers the region between the iol and hut operons,has been cloned and sequenced, creating a 99-kb contig fromthe gnt operon to the wapA locus. This region (23351 bp) contains25 complete open reading frames (ORFs; genes) including deoR,dra, nupC and pdp and two partial ones. The region (5140 bp)containing these four genes, being also sequenced by H. H. Saxildet al., was sequenced by subjecting a long polymerase chainreaction product to random sequencing using phage M13mp19. However,we could detect no conflict, between two independently determinedsequences, which could be attributed to our sequencing method.A homology search for the 24 newly identified gene productsrevealed significant homology to known proteins in 14 of them.It was notable that three proteins, encoded by the successivegenes (yxeMNO), exhibited meaningful homology to the E. coliGlnHPQ products constituting a periplasmic ATP-dependent transportsystem for glutamine.     

Single-Seeded Fruits and Seedling Establishment in Dalbergia miscolobium Benth. (Papilionaceae)1

Dalbergia miscolobium (Papilionaceae) is a tree of the Brazilian cerrado that produces ovaries with two ovules. Only one ovule usually matures, but when two mature, they are smaller than seeds of single-seeded pods. Germination percentage was lower in small seeds than in medium or large seeds. In general, small seeds gave rise to smaller seedlings (dry mass) than did medium and large seeds. The root/shoot ratio, however, was very similar for the first six months, indicating that this ratio is consistent across seedling sizes. There was no correlation between seed size and relative growth rate. Single-seeded fruit production in D. miscolobium resulted in greater seed reserves and increased fruit dispersal distance; single-seeded fruits were lighter than double-seeded ones. Together, these two features should increase the probability of successful seedling establishment of seeds from single-seeded versus double-seeded fruits.     

RT1.P, rat class Ib genes related to mouse TL: evidence that CD1 molecules but not authentic TL antigens are expressed by rat thymus

 CD1 and TL were once thought to be genetic homologues because of their thymus-specific expression. We investigated their equivalents in the rat to clarify whether their structure and pattern of expression are conserved in rodents. Two rat class Ib genes, containing 3′ sequences very similar to mouse TL, were identified and designated RT1.P. Neither of them, however, can encode ordinary class I molecules due to the accumulation of harmful mutations in the 5′ regions that are unique to RT1.P, while the 3′TL-like regions still retain protein-coding capacity. Comparison of the structural organization of three types of TL family genes, which include mouse T3/T18-encoding TL antigens, mouse T1/T16, and rat RT1.P1/P2 pseudogenes, revealed the presence of a clear demarcation between the type-specific and TL-specific sequences at intron 3. This finding suggests that recombination plays an important role in creating the TL family genes in rodents. Characteristic features of TL, such as a low level of polymorphism and linkage to the major histocompatibility complex, were also observed in the rat. On the other hand, rat CD1 molecules were expressed at a high level on the surface of thymocytes. Absence of authentic TL antigens and thymic expression of CD1d molecules in the rat suggest the plasticity and conservation of class Ib genes in rodent evolution. Functions of TL may be substituted with CD1 or other class Ib molecules expressed by rat thymus. Received: 16 December 1996 / Revised: 11 March 1997