Strand Of Stem Research Articles

Trichostomum tenuirostre var. gemmiparum (Schimp.) Zand. New to Japan

The distribution of Trichostomum tenuirostre (Hook. & Tayl.) Lindb. var. gemmiparum (Schimp.) Zand. is extended to eastern Asia. While examining a Japanese series of specimens from TNS determined as Tortella japonica (Besch.) Broth., a collection was discovered to have smooth, multicellular, dark orange, thick-walled gemmae. That the specimen had gemmae was indicated on the packet, probably by K. Saito, from whose herbarium many of the specimens examined derived. Since the specimen was not Tortella japonica, having no autoicous buds and lacking other characters of that species, further examination indicated the specimen was in fact Trichostomum tenuirostre (Hook. & Tayl.) Lindb., which has a described variety bearing gemmae, the var. gemmiparum (Schimp.) Zander. This variety has been recently treated by Zander (1994) for Mexico as Oxystegus tenuirostris (Hook. & Tayl.) A. Smith var. gemmiparus (Schimp.) Zand. Specimens from eight states in that country are known, with additional stations in Cuba, Haiti, and Brazil in the New World, and Europe and India in the Old. The present record extends the known distribution of this variety to eastern Asia. The species, however, is so variable and so easily confused with other species, primarily of the genus Tortella, that it is likely the variety is as widespread as the species. Noguchi (1988) did not mention gemmae in his treatment of Oxystegus for Japan. The problematical nature of the placement of Trichostomum tenuirostre is evident in his justification for keeping that species in Oxystegus, because of the absence of a strand in [the] stem. That Trichostomum tenuirostre has no strand was also asserted by Saito (1975). The Japanese specimen of the var. gemmiparum under discussion does, in fact, have a stem strand, which may account for its initial determination as Tortella japonica, which possesses that feature in addition to having a poorly defined region of basal cell differentiation. That the strand is variably present in Trichostomum tenuirostre in Europe has been noted by Hilpert (1933, p. 588) being large and well-defined to absent: gross und gut begrenzt, and fehlend. Flowers (1973) described the species from Utah in the United States as having central strand present, often weak or sometimes lacking. Of four of the specimens from Japan redetermined as Trichostomum tenuirostre, three possessed definite strands in addition to the specimen of the variety being discussed. Since known populations of var. gemmiparus include those with fruiting plants (Zander 1978), one cannot associate the production of gemmae exclusively with depauperate conditions; these plants may develop two distinct strategies for dispersal in the same population. The Japanese specimen was without fruit. For an extensive treatment of this plant and its nomenclature see Zander (1978). Illustrations of the gemmae are provided in Zander (1978; 1994). Specimen examined.-JAPAN Tokyo, Okutama, Nippara, Ogawadani valley, ca 1,000-1,700 m, on decayed wood, K. Saito 10306, Nov. 5, 1971 (TNS).

Expression of rice OSH1 gene is localized in developing vascular strands and its ectopic expression in transgenic rice causes altered morphology of leaf

Transgenic rice plants (Oryza sativa cv. Nipponbare) carrying 1 or 2 copies of a rice homeobox gene, OSH1, under the control of the CaMV 35S promoter were generated. The transgene caused altered morphology of leaf, such as ligule-replacement and abnormal division of sclerenchyma cells. The phenotype of these leaves resembles that of maize leaf morphological mutant, Knotted 1, which is caused by duplication of the KN1 gene (Veit et al., 1990). The in situ hybridization analysis has revealed that the expression of endogenous OSH1 is mainly localized in developing vascular strands of stem. We have discussed the biological roles of OSH1 in rice based on these results.

Human immunodeficiency virus rev protein recognizes a target sequence in rev-responsive element RNA within the context of RNA secondary structure

Human immunodeficiency virus type 1 Rev protein modulates the distribution of viral mRNAs from the nucleus to the cytoplasm by interaction with a highly structured viral RNA sequence, the Rev-responsive element (RRE). To identify the minimal functional elements of RRE, we evaluated mutant RREs for Rev binding in vitro and Rev response in vivo in the context of a Gag expression plasmid. The critical functional elements fold into a structure composed of a stem-loop A, formed by the ends of the RRE, joined to a branched stem-loop B/B1/B2, between bases 49 and 113. The 5' 132 nucleotides of RRE, RREDDE, which possessed a similar structure, bound Rev efficiently but were nonfunctional in vivo, implying separate binding and functional domains within the RRE. Excision of stem-loop A reduced Rev binding significantly and abolished the in vivo Rev response. The B2 branch could be removed without severe impairment of binding, but deletions in the B1 branch significantly reduced binding and function. However, deletion of 12 nucleotides, including the 5' strand of stem B, abolished both binding and function, while excision of the 3' strand of stem B only reduced them. Maintenance of the native RRE secondary structure alone was not sufficient for Rev recognition. Many mutations that altered the primary structure of the critical region while preserving the original RNA conformation were Rev responsive. However, mutations that changed a 5'..CACUAUGGG..3' sequence in the B stem, without affecting the overall structure abolished both in vitro Rev binding and the in vivo Rev response.