No description available.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Thesis (Ph. D.)--University of California, 1917. / Cover title. University of California publications in botany, v. 5, no. 12, March 6, 1918, with a special thesis t.p. dated May, 1917, attached to the cover-title. "Literature cited": p. 418-419.

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Septins are evolutionarily conserved proteins with roles in chromosome congression and segregation, cytokinesis and microtubule destabilization. Septins form homo- and hetero-oligomeric complexes, which are thought to act as dynamic scaffolds. We identified SEPT2/9/11/10 as novel interacting partners of adenomatous polyposis coli (APC), a bona fide tumor suppressor. Since septins and APC have similar roles and knockdown phenotypes, I sought to determine if they work together to perform their cellular functions. I showed that APC co-immunoprecipitates with endogenous septins in colon cancer cell lines. Using siRNA, I found that SEPT2 and APC may function within the same pathway to regulate DNA congression and segregation. Co-depleting SEPT9 with APC slightly alleviates the chromosome congression and segregation defects caused by siAPC alone. siSEPT9 increased abscission times, which was rescued by co-depleting APC. Future studies should elucidate the significance of the rescue data obtained upon APC and SEPT9 co-depletion and APC’s interactions with SEPT10/11.

Septins are evolutionarily conserved proteins with roles in chromosome congression and segregation, cytokinesis and microtubule destabilization. Septins form homo- and hetero-oligomeric complexes, which are thought to act as dynamic scaffolds. We identified SEPT2/9/11/10 as novel interacting partners of adenomatous polyposis coli (APC), a bona fide tumor suppressor. Since septins and APC have similar roles and knockdown phenotypes, I sought to determine if they work together to perform their cellular functions. I showed that APC co-immunoprecipitates with endogenous septins in colon cancer cell lines. Using siRNA, I found that SEPT2 and APC may function within the same pathway to regulate DNA congression and segregation. Co-depleting SEPT9 with APC slightly alleviates the chromosome congression and segregation defects caused by siAPC alone. siSEPT9 increased abscission times, which was rescued by co-depleting APC. Future studies should elucidate the significance of the rescue data obtained upon APC and SEPT9 co-depletion and APC’s interactions with SEPT10/11.

Fruit thinning is critical to the success of apple industry because most apple trees are prone to biennial bearing characterized by heavy bloom and over-cropping in the "on" year and low or no cropping in the "off" year. Fruit thinning can improve fruit size, increase return bloom, and reduce alternate bearing habit of apple trees. Chemical thinning has been widely used as a horticultural practice by growers for years in apple and other fruit production. However, its thinning results are often variable and very difficult to predict since parameters as well as their interactions (e.g. concentration, environmental condition, cultivar response) that affect thinning effectiveness have been poorly defined and the regulatory mechanisms at molecular level remain to be illustrated. Therefore, the purpose of this study is to characterize the physiological and molecular responses of the apple trees to the thinning treatments, and then use key genes as molecular markers for screening potential thinning agents. The long-term goal is to understand how the applied chemicals and environmental factors interact and regulate key regulatory genes as well as the thinning effectiveness during thinning process, and establish a predictable model for the improvement of fruit thinning consistency and effectiveness in apple and other fruit trees. Effects of naphthaleneacetic acid (NAA), shading, amimoethoxyvinylglycine (AVG) and 1-methylcyclopropene (1-MCP) on young apple fruit abscission, leaf and fruit ethylene production, and the expression of genes related to ethylene biosynthesis, perception and cell wall degradation were examined in "Golden Delicious" apples (Malus x domestica borkh.). NAA at 15 mg·L-1 and shading increased fruit abscission and ethylene production of leaves and fruit when applied at a 12-mm stage of fruit development, whereas AVG, an inhibitor of ethylene biosynthesis, at 250 mg·L-1 reduced NAA-induced fruit abscission and ethylene production of leaves and fruit. 1-MCP at 160 mg·L-1 had no effect on fruit abscission but induced ethylene production by both leaves and fruit. Changes in the gene expression pattern responding to each treatment were analyzed by real-time quantitative PCR. NAA treatment was found to enhance the expression of genes related to ethylene biosynthesis (MdACS5A, MdACS5B and MdACO1) and perception (MdETR1, MdETR1b, MdETR2, MdERS1 and MdERS2). AVG reduced NAA-induced expression of these genes except for MdERS2 in the fruit abscission zone (FAZ). NAA increased the expression of a polygalacturonase gene (MdPG2) in the FAZ but not in the fruit cortex (FC), whereas AVG reduced NAA-enhanced expression of MdPG2 in the FAZ. These results suggest that ethylene biosynthesis, ethylene perception, and MdPG2 gene are involved in young fruit abscission caused by NAA. On the other hand, 1-MCP did not affect the expression of MdACS5A and MdACS5B in the FAZ, although it enhanced the expression of these two genes in the FC from 6 to 24 hours post-treatment. The expression of MdACO1 in both tissues was increased by 1-MCP after 3 or more days post-treatment. 1-MCP had only a small influence on the expression of most ethylene receptor genes, with the exception of MdETR1, which was up-regulated in the FC to a level similar to that observed for NAA treatment. In response to 1-MCP, in the FAZ, the expression of MdCel1 and MdPG2 was up-regulated at the beginning and the end, respectively, of the experiment, but otherwise remained at or below control levels. 1-MCP did not inhibit NAA-induced abscission of young apple fruit, suggesting that abscission does not solely depend on ethylene signal transduction, or that the periods of effectiveness for 1-MCP and ethylene were asynchronous in this study. Gene expression analysis also revealed that both NAA and shading enhanced the expression of gene related to ABA biosynthesis in the FAZ, which suggested the involvement of ABA in young fruit abscission. Global gene expression profile during young fruit abscission was analyzed using an apple oligonucleotide microarray. More than 700 genes were identified with reproducible changes in transcript abundance in the FAZ after NAA treatment. Genes associated with abscission, ethylene, ABA, cell wall degradation, mitochondrial activity, glycolysis, lipid catabolism, secondary metabolism, abiotic stress, and apoptosis were upregulated, while genes involved in regulation of cell cycle, cell wall biosynthesis, photosynthesis, carbon fixation, chromatin assembly, auxin transport/efflux, cytoskeleton function, and flower development were generally downregulated. Comparison of changes in the gene expression patterns during NAA-induced fruit abscission with shading-induced fruit abscission revealed similarities, but also considerable differences. The data suggested that young fruit were shutting down growth and energy production and undergoing a certain kind of programmed cell death (PCD) induced by these different stimuli. Gene expression analysis in abscising young fruit revealed that photosynthesis, carbon utilization, and ABA/ethylene pathways appeared to operate in both NAA- and shading-induced fruit abscission. However, more sugar signaling genes were regulated in shading-induced fruit abscission, compared to NAA-induced fruit abscission. / Ph. D.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20447号 / 農博第2232号 / 新制||農||1050(附属図書館) / 学位論文||H29||N5068(農学部図書室) / 京都大学大学院農学研究科農学専攻 / (主査)教授 北島 宣, 教授 田尾 龍太郎, 教授 土井 元章 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

L’abscission des organes chez les végétaux est hautement régulée au cours du développement. Ce processus physiologique qui consiste à diminuer l’adhésion entre deux cellules adjacentes dépend de l’environnement, du stress, de l’attaque de pathogènes ou encore de l’état physiologique de la plante. L’abscission du fruit et de la graine jouent un rôle déterminant dans le cycle de vie de la plante et en particulier, un rôle central dans la dispersion des graines. C’est également un caractère commun de domestication avec des conséquences économiques pour la plus part des espèces cultivées. Le palmier à huile (Elaeis guineensis) est largement cultivé dans toutes les zones tropicales et l’huile de palme représente aujourd’hui plus d’un tiers des huiles végétales produites dans le monde. La maturation des fruits au sein des régimes est asynchrone. Ainsi, les fruits les plus murs tombent avant le murissement complet du régime, entrainant une baisse du rendement d’une part et rendant leur collecte manuelle fastidieuse et couteuse d’autre part. Dans ce context, le contrôle ou la réduction de la chute des fruits permettrait une meilleure gestion de la récolte à des couts réduits. Dans le cadre de cette étude, un protocole de phénotypage du processus d’abscission du fruit du palmier à huile a été développé et utilisé pour identifier des génotypes à faible ou retard d’abscision des fruits arrivés à maturité. En parallèle, des analyses comparatives de transcriptomes et de protéomes issus de la zone d’abscission (ZA) du fruit ont été conduites tout au long du processus de séparation cellulaire, déclenché au laboratoire par un traitement à l’éthylène ou bien de manière naturelle au champ. Au total 1957 gènes présentent une expression différentielle significative dans la ZA du fruit au cours du processus d’abscission induit par l’éthylène. Parmi ces gènes, 64 sont spécifiquement (ou majoritairement) exprimés dans la ZA des fruits arrivés à maturité par comparaison avec les tissus où le processus de séparation cellulaire n’est pas observé (pédicelle et mésocarpe des fruits murs ; ZA non fonctionnelle des fruits immatures). Le profil d’expression de ces 64 gènes candidats a été également analysé dans la ZA des fruits mûrs prélevés au champ, afin de conforter leur rôle potentiel au cours de l’abscission déclenchée naturellement. Ainsi, en utilisant les nouvelles technologies de séquençage du transcriptome et du protéome, couplées à une analyse biochimique et cellulaire des modifications de la paroi dans la ZA, ce travail a permis de mettre en évidence la conservation de certains processus moléculaires associés à l’abscission des organes chez les monocotylédones par comparaison avec les espèces modèles dicotylédones, telles que la tomate et Arabidopsis. Par exemple, l’identification de gènes codant des polygalacturonases très proches de celles qui sont impliquées dans l’abscission de la fleur chez Arabidopsis suggère la conservation de leur fonction dans l’hydrolyse de la pectine des cellules des ZA, malgré la divergence phylogénétique entre les espèces. Enfin, ce travail a permis également d’identifier de nouveaux régulateurs associés au processus de séparation cellulaire et fournir une liste de gènes associés à des processus biologiques étroitement liés à la fonction de la ZA chez le fruit du palmier à huile. / Plant organ abscission is a complex developmental process that involves cell separation regulated by the environment, stress, pathogens and the physiological status of the plant. In particular, seed and fruit abscission play a central role in seed dispersion and plant reproductive success, and are common domestication traits with important agronomic consequences for many crop species. Oil palm (Elaeis guineensis) is cultivated throughout the tropical regions as one of the most economically important oil crop species in the world. The unsynchronized ripening of the oil palm fruit bunch leads to the abscission of the ripest fruit and consequently high labor cost for harvest and loss of yield. In this context, the control of oil palm ripe fruit abscission is an important agricultural concern for the cultivation of oil palm in a sustainable and cost effective way. In the present study, a protocol to phenotype the oil palm fruit abscission process was developed and used to identify a tree in the field that does not undergo ripe fruit abscission. In parallel, transcriptome and proteome analyses of the oil palm ripe fruit abscission zone (AZ) during abscission induced experimentally by ethylene compared to the AZ undergoing natural abscission in the field was performed. A total of 1,957 candidate genes were identified statistically as differentially expressed in the ripe fruit AZ during ethylene-induced abscission. Furthermore, a total of 64 of these differentially abundant candidates were statistically specific or enriched at least during one time point of the ethylene induced abscission, compared to their profiles in the AZ of immature fruit and the pedicel of ripe fruit, where cell separation is not observed. The profiles of these gene candidates were examined in the ripe fruit AZ undergoing natural abscission in the field to validate their potential role during abscission. Finally, the profiles of selected candidate genes were then examined in the AZ of the tree observed not to undergo fruit abscission in the field. The combined approaches provide evidence of wide scale conservation of the molecular components involved in organ abscission of this monocot compared with the model dicot plants tomato and Arabidopsis. For example, the identification of polygalacturonases very similar to those that function during Arabidopsis floral organ abscission suggests a conservation of the components for pectin disassembly despite the phylogenetic distance between these species. In addition, the data from the global analysis and complementary molecular, cellular and biochemical approaches suggest novel components and provide a robust list of genes and processes important for AZ function during ripe fruit abscission of this important monocot crop species.

No description available.