John Gordon Torrey (1921?1993) (original) (raw)
Related papers
2006
Raffinose family oligosaccharides (RFOs) are involved in the storage and transport of carbon and serve as compatible solutes for protection against abiotic stresses like drought or cold. RFOs are usually transported in plant species that load sugars symplastically into the phloem. Loading probably occurs by a polymer trapping mechanism which establishes a concentration gradient of assimilates between the mesophyll and the vasculature. Transgenic approaches have demonstrated phloem transport of small molecules produced in the companion cells of apoplastic loading species, but these molecules have been non-native transport substances to plants. In this study, transgenic potato plants with constitutive or companion cell specific overexpression of galactinol synthase (GS) or GS plus raffinose synthase (RS) are characterized, which together provide new insights into the metabolism and transport of RFOs in plants. It is demonstrated that raffinose and galactinol are both transported in the phloem and that, whilst the effect of GS overexpression is promoter-independent, that of RS is dependent on the promoter used. The presence of significant amounts of galactinol in the phloem is shown and also that transgenic potato is unable to transport large amounts of raffinose despite high RS expression and substrate concentrations. These data indicate that there may be additional features of intermediary cells, the specialized companion cells of RFO transporting plants, required for significant RFO synthesis and transport that are currently not well-understood.
2013
A cDNA clone, designated as PvNAS2, encoding asparagine amidotransferase (asparagine synthetase) was isolated from nodule tissue of common bean (Phaseolus vulgaris cv. Negro Jamapa). Southern blot analysis indicated that asparagine synthetase in bean is encoded by a small gene family. Northern analysis of RNAs from various plant organs demonstrated that PvNAS2 is highly expressed in roots, followed by nodules in which it is mainly induced during the early days of nitrogen fixation. Investigations with the PvNAS2 promoter gusA fusion revealed that the expression of PvNAS2 in roots is confined to vascular bundles and meristematic tissues, while in root nodules its expression is solely localized to vascular traces and outer cortical cells encompassing the central nitrogen-fixing zone, but never detected in either infected or non-infected cells located in the central region of the nodule. PvNAS2 is downregulated when carbon availability is reduced in nodules, and the addition of sugars to the plants, mainly glucose, boosted its induction, leading to the increased asparagine production. In contrast to PvNAS2 expression and the concomitant asparagine synthesis, glucose supplement resulted in the reduction of ureide content in nodules. Studies with glucose analogues as well as hexokinase inhibitors suggested a role for hexokinase in the sugar-sensing mechanism that regulates PvNAS2 expression in roots. In light of the above results, it is proposed that, in bean, low carbon availability in nodules prompts the downregulation of the asparagine synthetase enzyme and concomitantly asparagine production. Thereby a favourable environment is created for the efficient transfer of the amido group of glutamine for the synthesis of purines, and then ureide generation.
2006
The involvement of polyamines (PAs) in the interaction between Pinus sylvestris L. seedlings and an ectomycorrhizal fungus Suillus variegatus (Swatz: Fr.) O. Kunze was studied in an in vitro cultivation system. PA concentrations in seedlings were analysed after 1, 3, and 5 weeks in dual culture with S. variegatus, and changes in PA pools were compared with the growth of the seedlings. Pinus sylvestris arginine decarboxylase (ADC) and S. variegatus ornithine decarboxylase (ODC) mRNA transcripts were localized during the formation of mycorrhizas. During mycorrhiza formation, Suillus variegatus ODC transcripts were found in developing hyphal mantle and Hartig net, and P. sylvestris ADC transcripts in specific root parenchyma cells adjacent to tracheids and in mitotic cells of the root apical meristem. However, no unambiguous difference in ADC transcript localization between inoculated and non-inoculated roots was observed. Regardless of the unchanged distribution of ADC transcripts, inoculation with S. variegatus increased free putrescine, spermidine, and spermine concentrations in roots within the first week in dual culture. The concentration of free and conjugated putrescine and conjugated spermidine also increased in the needles due to the fungus. The fungus-induced lateral root formation and main root elongation were greatest between the first and third week in dual culture, coinciding with retarded accumulation or a decrease of free PAs. These results show that accumulation of PAs in the host plant is one of the first indicators of the establishment of ectomycorrhizal interaction between P. sylvestris and S. variegatus in the in vitro system.
Section 4 - Root physiology and plant structure
Biologia Plantarum, 1992
Biol. Plant. 34 (Suppl.): 523, 1992 Explants from single trees of Abies concolor (Gord. et Glend) Lindl. • Abies grandis (mature embryo), Quercus robur L. (embryonic axis, young stem segments), Quercus rubra L. (young stem segments) and Castanea sativa L. (embryonic axis of mature embryo) were cultured on a callusinducing medium with NAb, or IBA (in Castanea) and BAP. Differentiation of tracheids tn both callus and explant tissues was preceeded by formation of cambium-like cells forming wound procambium zones of different shape. These zones produced tracheidal cells either on their convex side (cambium near to callus surface) or concave side (virtually wound cambium zones), where tracheid nests were produced. These were composed of irregulary arranged short or long and wound tracbeids surrounded by cells of the wound cambium. Tracheid nests originated in callus produced on hypocotyl-radicula region ofAbies explants were composed of nodal tracheids irregular in shape surrounded by the layer of the meristematic cells isodiametric in shape, capable of differentiation into tracheid cells. These tracheids as well as others differentiated in Abies explants had thickened secondary side walls with large circular bordered pits and sometimes, in addition, wound helical thickenings. On the other hand, in tracheids differentiated in callus of Quercus sp. and Castanea small circular or oval non-bordered pits or step-like thickening of secondary wail prevailed.
2013
Transgenic tomato [Lycopersicon esculentum (=Solanum lycopersicum)] lines overexpressing tomato PHYA, PHYB1, or PHYB2, under control of the constitutive double-35S promoter from cauliflower mosaic virus (CaMV) have been generated to test the level of saturation in individual phytochrome-signalling pathways in tomato. Western blot analysis confirmed the elevated phytochrome protein levels in dark-grown seedlings of the respective PHY overexpressing (PHYOE) lines. Exposure to 4 h of red light resulted in a decrease in phytochrome A protein level in the PHYAOE lines, indicating that the chromophore availability is not limiting for assembly into holoprotein and that the excess of phytochrome A protein is also targeted for light-regulated destruction. The elongation and anthocyanin accumulation responses of plants grown under white light, red light, far-red light, and end-of-day far-red light were used for characterization of selected PHYOE lines. In addition, the anthocyanin accumulation response to different fluence rates of red light of 4-d-old dark-grown seedlings was studied. The elevated levels of phyA in the PHYAOE lines had little effect on seedling and adult plant phenotype. Both PHYAOE in the phyA mutant background and PHYB2OE in the double-mutant background rescued the mutant phenotype, proving that expression of the transgene results in biologically active phytochrome. The PHYB1OE lines showed mild effects on the inhibition of stem elongation and anthocyanin accumulation and little or no effect on the red light high irradiance response. By contrast, the PHYB2OE lines showed a strong inhibition of elongation, enhancement of anthocyanin accumulation, and a strong amplification of the red light high irradiance response.
2000
Documenting the history of an organization is beneficial as a retrospective and as an aid in making wise decisions for the future. Dr. E.S. Luttrell penned, apparently under some duress, the first comprehensive historical account of the units of plant pathology at The University of Georgia. Although Dr. Luttrell did not view his account as a true history, it likely provides the most insightful perspective on how we got on the road we are today. That document was published in 1985 as Special Publication 35 of The Georgia Agricultural Experiment Stations and entitled "An Account of the Origins and Development of Plant Pathology in The University of Georgia and the Several Experiment Stations." That Special Publication is no longer in press, but the contents are reproduced herein. Drs. Richard Hanlin, Donald Sumner and Jerry Walker were kind in taking the time to provide an account of changes that occurred at the Athens, Tifton and Griffin campuses, respectively, between 1985 and 1999. Thus, this document provides a collective perspective on the history of our current status as a Department of Plant Pathology in the College of Agricultural and Environmental Sciences at The University of Georgia. My role in this process has been one of collector, not editor. As an addendum to Special Publication 35, I would like to note the contributions of Ms. Gwendolyn Burton Caldwell. Ms. Caldwell, at the time Ms. Burton, was a member of the faculty in the early 1940s and worked with Dr. Julian H. Miller. Ms. Caldwell was co-author on several significant papers on the life histories and morphology of ascomycetes that led to the foundation of using the developmental morphology and the internal structure of the ascocarp as a basis for classifying these fungi. These papers included:
Journal of Experimental Botany REVIEW ARTICLE
1996
New tools of microscopy, molecular biology, and genetics are making it possible for biologists to study roots with new vigour. Such investigations have enabled plant biologists to notice the symmetry, pattern, and simplicity of root structures so that there is now an exciting rebirth in the study of roots. The literature of root biology, development and structure is vast. In this short review we will concentrate on describing our notion of how roots are organized structurally, and then discuss what is known about tissue- and zone-specific gene expression in roots. Key words: Root apex, root anatomy, root development, gene expression. Root organization