Thesis (Ph.D.)--Murdoch University, 2003. / Thesis submitted to the Division of Science and Engineering. Bibliography: leaves 229-232.

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Dr. Hank W. Bass, Florida State University, College of Arts and Sciences, Dept. of Biological Science. Title and description from dissertation home page (viewed Sept. 19, 2005). Document formatted into pages; contains viii, 93 pages. Includes bibliographical references.

Mesorhizobium loti possesses a symbiosis island (ICEMlSym[R7A]) that confers upon the bacterium the ability to form a symbiotic association with legumes of the genus Lotus. Nodulation (nod, nol and noe) genes located on the ICEMlSym[R7A] encode enzymes that are responsible for the production of a species-specific signaling molecule, named Nod factor. Perception of Nod factors by plant receptors triggers several plant responses and facilitates bacterial invasion, leading to the formation of root nodules. The studies in this thesis aimed to examine the impact of various structural components of the M. loti Nod factor on host specificity and recognition within Lotus species. The minimal gene requirement for eliciting nodule development on Lotus plants was also determined. The M. loti strain R7A Nod factor has a backbone of five N-acetyl-D-glucosamine (GlcNAc) residues. The non-reducing terminal GlcNAc residue carries an acyl chain of either a vaccenic acid (C[18:1]) or palmitic acid (C[16:0]), a carbamoyl group and a methyl group, while an acetylfucose is present at the reducing terminus. Analysis of loss-of-function [Delta]nodZ and [Delta]nolL mutants showed that the acetylfucose at the reducing terminus was required for efficient nodulation of Lotus species, especially during the initiation of infection threads and for induction of symbiotic gene, NIN. Upon inoculation with R7A[Delta]nodZ, nodulation of Lotus corniculatus and L. filicaulis was significantly delayed and reduced, while only a delay in the onset of nodulation was observed with L. japonicus. Interestingly, nodulation of L. burttii induced by R7A[Delta]nodZ was as efficient as that induced by R7A. Hence, the absolute requirement for the acetylfucose during nodulation was host-dependent. In planta complementation and domain swap experiments using transgenic L. japonicus nfr1 and nfr5 mutants were employed to investigate the role of the reducing terminal acetylfucose in the perception of Nod factor. Nodulation of complemented L. japonicus nfr1 and nfr5 mutants inoculated with R7A[Delta]nodZ was poor, whereas similar plants inoculated with R7A nodulated well. This suggests that the in planta complementation was inefficient and as a result accentuated the effect of the acetylfucose on the Nod factor recognition. The responses of recombinant inbred lines (RILs) derived from a cross between L. filicaulis and L. japonicus to inoculation with strain R7A[Delta]nodZ suggested that at least two genetic loci on chromosome 4, in addition to the Nfr1 and Nfr5 genes, contribute to Nod factor perception and in particular the host-specific recognition of the acetylfucose, This suggests the involvement of multiple receptors or a receptor with multiple components in the perception of Nod factors. A gain-of-function study demonstrated that the presence of nodulation genes alone in nonsymbiotic mesorhizobia was sufficient to induce nodulation and bacteroid formation on Lotus plants, indicating that no other ICEMlSym[R7A] genes were required for infection thread formation or bacterial release. Nodulation assays of four Lotus species indicated host-specific requirements for nodulation genes. The presence of the nodA, nodC, nodD1, nodD2, nodZ, noeL and nolK genes was sufficient to permit nodulation of L. burttii, but was insufficient to induce nodulation of L. japonicus, L. corniculatus and L. filicaulis. The importance of the carbamoyl and methyl groups, and the influence of Nod factor concentration during nodulation were also implicated in this study. A model for the Nod factor perception in Lotus was proposed.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Plant Science, Waite Agricultural Research Institute, 1993.

Thesis (Ph. D.)--Oregon State University, 1999. / Typescript (photocopy). Includes bibliographical references (leaves 101-118). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 145-156). Also available on the World Wide Web.

Gene expression in two different genotypes of alfalfa, salt-tolerant and salt-sensitive, was examined by studying differences in protein products coded for by poly(A+) RNA isolated from shoot and root tissue. Plants were grown in hydroponics under unstressed or salt-stressed conditions. Two salinity levels (low salt: 30 mM NaCl and 6 mM CaCl2 and high salt: 133 mM NaCl and 27 mM CaCl2) and one unstressed control were applied. The salt-tolerant genotype showed higher biomass accumulation than the salt-sensitive genotype under both control and salt-stressed conditions. The difference in biomass accumulation between the two genotypes was greatest at the highest salt level. The effect of salt stress on gene expression was studied via in vitro translation of poly (A+) RNA with (35S) -methionine. The labeling pattern was similar in all treatments when analyzed by one dimensional SDS-PAGE. However, a two dimensional analysis (isoelectric focusing followed by SDS-PAGE) showed that salt-stress induced a number of new proteins and repressed several others.

Thesis (Ph.D.)-- University of Adelaide, Dept. of Plant Science, 2001. / Includes bibliographical references (leaves 192-211).

Plant productivity is greatly affected by environmental stresses such as drought, salinity and insect herbivory. Plants respond and adapt to these stresses by exhibiting physiological as well as biochemical changes at the cellular and molecular levels in order to survive. Expression of a variety of genes which encode numerous membrane transporters have been demonstrated to be induced by these stresses in a variety of plants. The nutritional status of plants is controlled by these transporters, which are regulated by the transcription of the corresponding genes. In spite of these adverse stress effects on agricultural yield, only a few studies have focused on gene transcriptional and translational regulation of membrane transporters during environmental stress situations. Rice, like other plants, contains a number of sucrose transporters encoded by a family of genes. However, detailed knowledge of their roles, localization and regulation during environmental stress conditions is lacking. Bioinformatic tools were used to identify putative cis-acting regulatory elements that may be involved in the regulation of rice and Arabidopsis thaliana sucrose transporters. The possible cis-acting regulatory elements were predicted by scanning genomic sequences 1.5 kbp upstream of the sucrose transporter genes translational start sites, using Plant CARE, PLACE and Genomatix Matinspector professional data bases. Several cis-acting regulatory elements that are associated with plant development, plant hormonal regulation and stress response were identified, and were present in varying frequencies within the 1.5 kbp of 5′ regulatory region. The putative cis-acting regulatory elements that possibly are involved in the expression and regulation of sucrose transporter gene families in rice and Arabidopsis thaliana during cellular development or environmental stress conditions were identified as: A-box, RY, CAT, Pyrimidine-box, Sucrose-box, ABRE, ARF, ERE, GARE, Me-JA, ARE, DRE, GA-motif, GATA, GT-1, MYC, MYB, W-box, and I-box. Expression analysis was used to elucidate the role of rice (Oryza sativa L. cv Nipponbare) sucrose transporter (OsSUT) genes during drought and salinity treatments of three week old rice plants ( at four leaf stage) over a 10 days. Among the five rice OsSUT genes identified, only OsSUT2 was observed to be progressively up-regulated during drought and salinity treatments, while OsSUT1, OsSUT4 and OsSUT5 were expressed at low levels, and OsSUT3 showed no detectable transcript expression. Sucrose transport will be essential to meet the cellular energy demands and also for osmoprotectant activities during drought and salinity stresses. It therefore indicates that OsSUT2 which facilitates transport of sucrose from photosynthetic cells will be III essential for rice plants to cope with drought and salinity stresses, and cultivars with a higher OsSUT2 expression should be able to tolerate these environmental stresses better. The role of OsSUT in assimilate transport during rusty plum aphids (Hysteroneura setariae; Thomas) infestation on the leaves of three week old rice (Orzya sativa L. cv Nipponbare) cultivar plants, over a time-course of 1 to 10 days of treatments, was also examined by combination of gene expression and β-glucuronidase (GUS) reporter gene analysis. Real Time PCR analysis of the five OsSUT genes revealed that the expression of OsSUT1 was progressively up-regulated during the course of aphid infestation. OsSUT2 and OsSUT4 expression were comparatively low in both the control and treated plants. OsSUT5 showed no clear difference in transcript expression in both control and treated plants, while no detectable transcript expression of OsSUT3 could be found. The up-regulation of OsSUT1 gene was verified at protein level by western blot analysis in both the control and treated plants. OsSUT1 protein expression was found to increase with time during aphid infestation. A similar trend was noticeable in the control plants, however at a lower expression level. These demonstrate that the cellular expression of OsSUT1is regulated by both developmental and environmental factors. OsSUT1-promoter:::GUS reporter gene expression was observed within the vascular parenchyma and/or companion cells associated with phloem sieve elements of the large and small bundles in the phloem tissues of the flag leaf blade regions where feeding aphids were confined, which progressively increased with time of infestation. It is suggested that OsSUT1 may primarily play an essential role in phloem transport of assimilate to wounded tissues from adjacent health tissues or may be involved in the retrieval of assimilate back into the phloem to minimize loss caused by the infestation. Some OsSUT1-promoter:::GUS expression was also found in the metaxylem at 10 days after infestation, which could signify a recovery system in which sucrose lost into the xylem as a result of aphids feeding are retrieved back into the phloem through the vascular parenchyma. This was supported by the exposure of cut ends of matured OsSUT1-promoter:::GUS rice plant leaf to 2% sucrose solution. OsSUT1-promoter:::GUS expression was observed within the protoxylem, xylem and phloem parenchyma tissues. This indicates that sucrose translocating within the xylem tissues are retrieved into the phloem via the OsSUT1 localized within the parenchyma tissues. In conclusion, the differential expression and regulation of rice (Orzya sativa L. cv Nipponbare) sucrose transporters as reported here suggest that OsSUT2 and OsSUT1 were constitutively expressed compared to other rice sucrose transporters during drought and salinity, and rusty plum aphids (Hysteroneura setariae; Thomas) infestation stresses respectively. Thus, the expression and regulation of the sucrose transporters could be related to the physiological and nutritional requirements of the cells during plant developmental or environmental stress state that allows their differential expression.

Backcross populations (BC) from Medicago sativa L. x M. dzhawakhetica Bordz. hybrids were analyzed for chromosome number, fertility and morphological characteristics. Previously obtained F1 hybrids were recovered when diploid (2n = 2x = 16) M. sativa was crossed with tetraploid (2n = 4x = 32) M. dzhawakhetica. Resulting F1 hybrids were triploid (2n = 3x = 24), completely male sterile and had low levels of female fertility. Subsequent populations were obtained by successive backcrossing to unrelated (4x) M. sativa clones. The BC1 plants were pentaploid (2n = 5x = 40) and both male and female fertile. BC2 populations had chromosome numbers ranging from 2n = 32 to 48, and most plants (94% were male and female fertile. BC3 populations were tetraploid (2n = 32) or near tetraploid (2n = 33) and were morphologically similar to M. sativa. Preliminary analysis of mitochondrial nucleic acids by agarose gel electrophoresis, indicated biparental inheritance of this organelle in the F1 hybrids; however, further analysis provided inconclusive results.