Graduation date: 1993

Light is the fundamental source of energy and information throughout the plant life cycle. Light signals regulate plant architecture and branching, key processes that determine biomass production and grain yield. Low red (R) to far-red (FR) light ratios (R:FR) perceived by phytochromes serve as a warning signal about impending competition for light resources and lead to shade avoidance responses (SARs), including reduced branching. The R:FR regulates branching in both a bud autonomous and non-bud autonomous manner, however a detailed mechanistic understanding of the process remains unclear. We hypothesized that high R:FR promotes bud outgrowth by differentially regulating branching-related genes (transcriptome) within the axillary bud and that increased apical dominance under low R:FR or with phyB deficiency is mediated by auxin or other novel signal/s. We analyzed the branching phenotype of Arabidopsis Columbia-60000 ecotype in response to different R:FR treatments and conducted a microarray study to identify early (within 3 hours) changes in the transcriptome of buds from different rosette positions in response to altered R:FR. Physiological experiments were also conducted to determine if auxin concentration, transport rate, sensitivity, and establishment of an auxin transport stream were important in determining the branching phenotype of shade avoiding plants. The results revealed that the duration of low R:FR determines plant architecture and the branching phenotype and that bud outgrowth is regulated by the R:FR in a spatial and temporal manner. Low R:FR promoted the elongation of branches at top rosette nodes while it suppressed the outgrowth of axillary buds at lower nodes. High R:FR could reverse the effects of previous low R:FR by promoting the outgrowth of buds from lower axils within 24 hours of treatment. Transcriptomic analysis revealed that the R:FR differentially regulated the expression of genes related to hormone biosynthesis/transport/signaling, cell-cycle regulation and cell wall modification. Cis-elements responsive to light and hormone signaling pathways were overrepresented in several gene clusters. Apical dominance related studies discovered that loss of phyB function results in a slower auxin transport rate, fewer xylem parenchyma cells, and reduced sensitivity to auxin. These results, in addition to estimates of correlative inhibition, suggested that auxin is at least partially responsible for increased apical dominance under low R:FR or with phyB deficiency, but may be acting in conjunction with other undefined regulators.

The branching or tillering of crops is an important agronomic trait with a major impact on yield. Maintaining an appropriate number of branches allows the plant to use limited light resources and to produce biomass or yield more effectively. The branching process includes the initiation of the axillary meristem leading to bud formation and the further outgrowth of the axillary buds. Phytohormones, including cytokinins and auxin, are known to play major roles in regulating axillary bud outgrowth. Light signals, including light quantity and light quality, are among the most important factors regulating plant growth and are perceived by the action of specialized photoreceptors, including phytochromes. Phytochromes sense red (R) and far-red (FR) light and allow some plants to perceive and respond to competing neighbors by evoking the shade avoidance syndrome (SAS). One component of the SAS is inhibition of branching. Phytochrome B (phyB) is especially important in sensing shade signals and loss of phyB function results in a constitutive shade avoidance phenotype, including reduced branching. While it has been anecdotally reported that phyB-deficient Arabidopsis branches less than wild type, a detailed study of the defects in the process is lacking. In this research, the interactions between light signals, phytochromes and phytohormones in the regulation of branching were assessed using an integrated physiological, molecular and genetic approach.

Plants sense light intensity, quality and direction through a group of photoreceptors to modulate their growth and development. One family of photoreceptor is called phytochromes (phys) that perceives red and far red light. Phys transduce light signals via a sub-family of the basic Helix-Loop-Helix (bHLH) transcription factors called Phytochrome Interacting Factors (PIFs). PIFs function as negative regulators in the phy-mediated light signaling pathways. In darkness, PIFs regulate downstream gene expressions to inhibit photomorphogenesis. Upon light exposure, PIFs are phosphorylated and poly-ubiquitylated prior to their rapid degradation through the 26S proteasome pathway. One of the PIFs, PIF1, has the highest affinity for both phyA and phyB and also displayed the fastest degradation kinetics under both red and far red light. Here we showed that PIF1 directly and indirectly regulates key genes involved in chlorophyll biosynthesis to optimize the greening process in Arabidopsis. PIF1 binds to a G-box (CACGTG) DNA sequence element present in its direct target genes (e.g., protochlorophyllide oxidoreductase C, PORC) in darkness and regulates their expression. Structure-function studies revealed two separate regions called APB and APA necessary for binding to phyB and phyA, respectively, located at the amino-terminus and a novel phosphorylation site at the carboxy-terminus of PIF1. Both amino- and carboxy-terminal regions are necessary for the light-induced degradation of PIF1. However, the DNA binding is not necessary for the light-induced degradation of PIF1. Using a targeted systems biology approach, we identified new factors, HECATE proteins that promote photomorphogenesis by negatively regulating the function of PIF1. Moreover, we employed an unbiased genetic screening using luciferase imaging system to identify new mutants defective in the light-induced degradation of PIF1. The cloning and characterization of these mutants will help identify the factors, such as the kinase and E3 ligase, responsible for the light-induced degradation of PIF1. Taken together, these data revealed detail mechanisms of how PIF1 negatively regulates photomorphogenesis and how light induces rapid degradation of PIF1 to promote photomorphogenesis. / text

Methyl bromide fumigation, a common method used to combat soil borne pathogens in commercial tomato cultivation, was to be limited by the Montreal Protocol due to concerns of ozone depletion. Alternative methods to protect tomatoes against diseases include grafting. However, short grafted transplants may expose the scion to the soil. To avoid scion exposure, hypocotyl elongation of two tomato rootstocks 'Maxifort' and 'Aloha' via end-of-day far-red (EOD-FR) was examined in terms of light quality (red to far-red ratio, or R/FR) and dose (product of far-red intensity and duration). In EOD-FR light quality experiments, 'Aloha' seedlings were exposed to unfiltered and filtered incandescent light with an R/FR of 0.5 and 0.05 respectively. The resulting hypocotyl elongation was higher in filtered light than either the unfiltered light or the untreated control. Hypocotyl elongation response to EOD-FR dose in 'Aloha' and 'Maxifort' was affected by both far-red intensity and treatment duration. A saturating response was also found within a far-red dose between 0–8 mmol•m⁻²•d⁻¹ and modeled using non-linear regression with a three parameter Michaelis-Menten equation to estimate the far-red dose required to obtain near-maximum hypocotyl elongation for 'Aloha' and 'Maxifort'. The far-red dose required was affected by cultivar and experimental period. None of the EOD-FR treatments affected plant mass or stem diameter. To conclude, for maximum hypocotyl elongation using EOD-FR, the lower R/FR would increase the effectiveness of the treatment. The far-red dose should preferably be at 4–8 mmol• m⁻²•d⁻¹.

Made available in DSpace on 2014-06-11T19:23:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-02-17Bitstream added on 2014-06-13T18:50:05Z : No. of bitstreams: 1 simao_e_me_rcla.pdf: 593595 bytes, checksum: b07688759335c8b16d0507273cdcdc7e (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O objetivo deste trabalho foi conhecer os aspectos envolvidos na germinação de sementes de Tibouchina mutabilis (Vell.) Cogn. (Melastomataceae), espécie característica da encosta úmida da Serra do Mar que ocorre do Rio de Janeiro até Santa Catarina na floresta pluvial da encosta Atlântica. De acordo com a literatura, a espécie é encontrada quase que exclusivamente na mata secundária, onde chega por vezes constituir-se na espécie dominante. Os parâmetros analisados foram: porcentagem final de germinação, velocidade média, o tempo médio e o índice de sincronização e, para maturação, também foi analisada a morfologia do embrião. A faixa ótima de temperatura que proporcionou os melhores valores de porcentagem e velocidade de germinação foi de 25 a 30ºC e na alternância de temperaturas, sob fotoperíodo de 12 horas foi de 20-25°C. As sementes foram sensíveis a luz germinando preferencialmente sob fotoperíodos longos 8 a 12 horas, sendo a quantidade da luz fornecida, determinante na velocidade de germinação, enquanto que a qualidade da luz influenciou as porcentagens finais de germinação, que foi maior nas condições de fotoequilíbrio do fitocromo altos. As sementes embebem no escuro, mas não germinaram na ausência de um período mínimo de 96h de luz. A capacidade germinativa ocorreu com 14 dias pós-antese e a máxima germinação foi atingida aos 21 dias. Observou-se que o melhor indicador de maturação fisiológica para a espécie é o início da abertura natural das cápsulas. Estas características apresentadas indicam que T. mutabilis é uma espécie com características típicas de pioneira. / The objective of this work was to know the aspects involved in seed germination Tibouchina mutabilis (Vell.) Cogn. (Melastomataceae), feature species of Serra do Mar, occurring from Rio de Janeiro to Santa Catarina, Brazil in Atlantic Forest. The species is found mostly in secondary forest sometimes consisting the dominant species. It was analyzed the final percentage of germination, mean germination rate and daily relative frequency and the synchronization index; It was analyzed the morphology of the embryo and germination capacity during maturation. The range of optimum temperature to germination was of 25 to 30ºC and in the alternating temperature of 20-25°C. The seeds of T. mutabilis were sensitivity to the light, the germination happened preferentially under long photoperiod of 8 to 12h, increase in the light fluence increase the germination rate and increase in the photoequilibrium of phytochrome increase the final percentage germination. The seeds of the T. mutabilis imbibed in darkness, but did not germinate on absence of a minimum period of light 96 hours. The germination capacity appeared in 14 days stage of development, whose embryo in some seeds were partially developed, and the maximum germination capacity was reached in 21 days stage, whose embryo full up the capsule. The best indicator of physiological maturation to this specie is natural open beginning of the capsule. The results showed that T. mutabilis is a pioneer, absolute positive photoblastic specie.

Orientador: Rogério Falleiros Carvalho / Banca: Paulo Alexandre Monteiro / Banca: Davi Rodrigo Rossatto / Resumo: Embora os fitocromos pareçam ser importantes fotorreceptores que modulam a relação entre a fonte e o dreno, muito ainda é necessário explorar visto que essas moléculas podem acumular e agir tanto na parte aérea quanto na raiz. Dessa forma, objetivou-se neste trabalho estudar a função dos fitocromos na relação fonte-dreno em plantas de tomateiro (Solanum lycopersicum L. cv. Micro- Tom ou MT) explorando fisiológica, bioquímica, nutricional e anatomicamente o mutante deficiente na biossíntese dos fitocromos (aurea ou au), bem como utilizando o método da enxertia entre o mutante au e o controle MT. Foram realizados dois experimentos, sendo que o primeiro experimento utilizou-se o mutante au e o controle MT. Para o segundo experimento, foram realizados seis tratamentos, constituídos pelas combinações entre a planta controle e o mutante, bem como as testemunhas sem enxertia (MT, MT/MT, au, au/au, MT/au e au/MT) a fim de serem analisadas as seguintes respostas: massa seca da raiz (MSR), comprimento (CR), área (AR), diâmetro (DR) e densidade das raízes (DE), massa seca da parte aérea (MSA), alongamento caulinar (AC), área foliar total (AF), peso e diâmetro dos frutos (PF e DF), teor de sólidos solúveis (SS), acúmulo de nutrientes (AN), análise de plântulas (AP), teores dos pigmentos, amido, carboidrato e análises anatômicas. No primeiro experimento, comparado ao MT, o mutante au aumentou a AC, AN na parte aérea, amido e espessura do mesofilo, entretanto, houve uma redução d... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Although the phytochrome seems to be an important photoreceptor to modulate the relation between the source and the drain, much is still necessary to explore since these molecules can accumulate and act both in the shoot and in the root. Thus, the aim of this work was to study the role of phytochrome in the source-drain relation on tomato plants (Solanum lycopersicum L. cv. Micro-Tom or MT) exploring physiological, biochemical, nutritional and anatomically the deficient mutant in the phytochrome biosynthesis (aurea or au), as well as using the method of grafting between the mutant au and the MT control. Two experiments were conducted, and in the first experiment it were used the au mutant and the MT control. For the second experiment, it were carried out six treatments, consisting of combinations of the control plant and the mutant, as well as the controls without grafting (MT, MT/MT, au, au/au, MT/au and au/MT) in order to analyze the following responses: dry mass of root (DMR), length (L), area (A), diameter (D) and density of roots (DE), dry mass of shoot (DMS), stem elongation (SE), total leaf area (LA), weight and diameter of fruits (W and FD), solid soluble content (SS), nutrient accumulation (NA), seedlings analysis (SA), pigment content, starch, carbohydrate and anatomical analysis. In the first experiment, compared to the MT, the au mutant increased the SE, NA in the shoot, starch and thickness of the mesophyll, however, there was a reduction in the DMR, L, A, NA at the root, DMS, LA, carbohydrates and pigments. In the second experiment, based on the MT control there was a reduction in the DMR, L, DE, DMS and LA of Au/MT, while in MT/au there was a decrease in the DMR, L, DE, DMS, LA and FD. Based on changes in the growth, biochemical, nutritional and anatomical of the roots and the au stem observed in the first experiment ... (Complete abstract click electronic access below) / Mestre

Orientador: João Domingos Rodrigues / Banca: Ubirajara Contro Malavasi / Banca: Elisabeth Oriko Ono / Banca: Carmem Silvia Fernandes Boaro / Banca: José Antonio Proenço Vieira de Moraes / Resumo: A luz pode ser considerada um dos principais fatores ambientais no controle da germinação e desenvolvimento de diferentes espécies, principalmente em plantas nativas. Tendo em vista a importância da espécie Peltophorum dubium para a utilização no re-povoamento de áreas degradadas, arborização e paisagismo, avaliou-se o comportamento fisiológico de suas sementes analisando a influência da luz eo efeito de um protetor físico com diferentes filtros no processo germinativo, emergência, crescimento inicial e trocas gasosas de suas plântulas. Para tanto, frutos maduros de canafístula foram coletadas em diversas matrizes em setembro de 2007. Após a coleta, os frutos foram levados para o Laboratório de Interações Tróficas do Departamento de Botânica do Instituto de Biociência da Unesp/Botucatu onde foram beneficiadas e escarificadas. Desta forma, instalou-se os seguintes tratamentos: T 1- gerbox transparente; T2- gerbox transparente + celofane transparente; T3- gerbox preto; T4- gerbox preto + celofane transparente; T5- gerbox transparente + celofane azul e T6- gerbox transparente + celofane vermelho. Foram avaliadas as seguintes características: porcentagem de germinação, IVG, comprimentos de radícula, de epicótilo, de cotilédone e da plântula, massa seca, clorofilas a, b, totais e relação a/b. Em um segundo experimento realizado na área aberta do Departamento de Botânica (22° 52' de latitude, 48 ° 26' de longitude), no Instituto de Biociências, Unesp, Botucatu - SP, utilizando-se um protetor físico constituido por garrafas do tipo P.E.T. (Polietileno Teraftalato) com volume de 2500 mL sem fundo e sem tampa. Diferentes comprimentos de ondas luminosas foram obtidos acoplando as garrafas do tipo P.ET. com duas camadas de papel celofane com diferentes tonalidades (transparente, azul e vermelho). Desta forma, obtiveram-se os seguintes tratamentos: T1, ausência... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Light is considered one of the major environmental factors controlling the germination and development of different species, mainly native ones. Based on the importance of the species Peltophorum dubium for revegetation of degraded areas, tree planting and landscaping, this study evaluated germination, emergence, initial growth and gas exchanges of canafistula seedlings under light influence by using physical protectors presenting different filters. Thus, the following treatments were adopted: T1, transparent germination box; T2, transparent germination box + transparent cellophane; T3, black germination box; T4, black germination box + transparent cellophane; T5, transparent germination box + blue cellophane; T6, transparent germination box + red cellophane. The evaluated characteristics were: germination percentage, germination velocity index (GVI), radicle, epicotyl, cotyledon and seedling ngth, dry matter, total chlorophylls and their fractions a and b, and the ratio a/b. A second experiment was carried out in an open area from the Department of Botany (22° 52' S, 48 ° 26' W), Institute of Biosciences, Sao Paulo State University (UNESP), Botucatu, Sao Paulo State, Brazil, in which physical protectors corresponding to polyethylene terephthalate (PET)-type bottles (2500 mL) without lid and bottom were used. Different wavelengths were obtained when two layers of cellophane paper of different colors (transparent, blue and red) were added to the PET-type bottles. Thus, the following treatments ere established: T1, absence of physical protector (APP); T2, transparent physical protector (TPP); T3, transparent physical protector + blue cellophane (BPP); and T4, transparent physical protector + red cellophane (RPP). The experimental design was completely randomized, with 4 treatments x 6 evaluation times and 5 replicates. Emergence velocity index (EVI), seedling emergence, survival... (Complete abstract click electronic access below) / Doutor

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21595号 / 理博第4502号 / 新制||理||1646(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 寺嶋 正秀, 教授 林 重彦, 教授 竹腰 清乃理 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21250号 / 理博第4420号 / 新制||理||1634(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 長谷 あきら, 教授 鹿内 利治, 准教授 小山 時隆 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM