Search results
(881 - 887 of 887)
Pages
- Title
- MUTANT ANALYSIS OF A POLYOL MONOSACCHARIDE TRANSPORTER IN ARABIDOPSIS INVOLVED IN LIGNIFICATION
- Creator
- Tran, John Dang Khoa
- Date
- 2022
- Collection
- Electronic Theses & Dissertations
- Description
-
Monolignols have important roles in plant development and primarily serve as monomers for lignin polymerization in secondary cell walls. Monolignols are synthesized in the plant cytoplasm prior to entering the apoplast where oxidation occurs. Upon oxidation, monolignols are incorporated into the cell wall. Several mechanisms have been suggested to explain how monolignols cross the plasma membrane, including endocytosis, diffusion, and active transport. However, evidence for those models...
Show moreMonolignols have important roles in plant development and primarily serve as monomers for lignin polymerization in secondary cell walls. Monolignols are synthesized in the plant cytoplasm prior to entering the apoplast where oxidation occurs. Upon oxidation, monolignols are incorporated into the cell wall. Several mechanisms have been suggested to explain how monolignols cross the plasma membrane, including endocytosis, diffusion, and active transport. However, evidence for those models relied on theoretical calculations or produced results using in vitro approaches. Further, only one active transporter protein has been characterized to date. Yet, of the three monolignols tested, the transporter was only demonstrably shown to transport p-coumaryl alcohol, the least abundant monolignol present in Arabidopsis.Here we show that AtPMT4 is likely a monolignol transporter, particularly for the more abundant monolignols: coniferyl alcohol and sinapyl alcohol. Gene expression analysis performed on AtPMT4 in dicots and monocots shows coexpression with lignin biosynthetic genes. Cell-specific expression analysis of the inflorescence stem, a tissue that undergoes intense lignification to provide plant structural support, shows that AtPMT4 is expressed higher in cell types that lignify. We demonstrate that Arabidopsis Col-0 plants transformed with a CRISPR-Cas9 construct targeted near the TSS of AtPMT4, a member of the POLYOL/ MONOSACCHARIDE TRANSPORTER family, which is a subfamily of the MONOSACCHARIDE TRANSPORTER-LIKE family, displayed altered lignin phenotypes. We quantified the total lignin, free monomer subunits, and digestibility of the inflorescence stem in pmt4. Our studies show lower amounts of lignin and increased digestibility when AtPMT4 is mutated. Further, we show that pmt4 is sensitive to monolignols when grown in the presence of coniferyl alcohol. pmt4 displayed shorter root length compared to Col-0 at low concentrations of coniferyl alcohol. In conclusion, we provide evidence for an understanding of monolignol translocation and lignification by which transporters are likely involved in a proton-coupled manner.
Show less
- Title
- THE NUCLEO-CYTOPLASMIC FUNCTION OF ACTIN AND ACTIN DEPOLYMERIZATION FACTORS IN PLANT IMMUNITY
- Creator
- Li, Pai
- Date
- 2022
- Collection
- Electronic Theses & Dissertations
- Description
-
The plant immune system is a multi-phase complex network that involves the collaboration of multiple subcellular structures. In the past two decades, the core signaling pathways of the immune process, including pattern-triggered immunity (PTI), effector-triggered immunity (ETI), and systemic acquired resistance (SAR), as well as the behavior of organelles, have been revealed to a level of clarity that is able to describe a general and well-covered process of the immune response. However,...
Show moreThe plant immune system is a multi-phase complex network that involves the collaboration of multiple subcellular structures. In the past two decades, the core signaling pathways of the immune process, including pattern-triggered immunity (PTI), effector-triggered immunity (ETI), and systemic acquired resistance (SAR), as well as the behavior of organelles, have been revealed to a level of clarity that is able to describe a general and well-covered process of the immune response. However, there are still many events during the immune response that remain mysterious. For instance, while higher plants live a sessile lifestyle, there are countless intracellular motions mediated by the cytoskeleton (including its associated proteins) in response to the external triggers, such as the invasion of pathogens. As our knowledge of plant immunity accumulates, the deficiency in knowledge on how immune signaling regulates the behavior of the cytoskeleton as a critical aspect of defense response, howbeit, becomes more evident. Therefore, this is a field of research that calls for powerful toolboxes to facilitate the analysis of the cytoskeleton in the context of immunity, as well as instructive biological model(s) that guide the direction of the multifarious studies. In this dissertation, I focus on the summary and prospective discussion on the immune function of the actin cytoskeleton and, more importantly, describe my original studies on two major aspects of this topic. First, a prerequisite to functional study of the actin cytoskeleton in the cytoplasm is the ability to accurately describe the status of the cytoskeleton. To achieve this goal, I developed an algorithm, namely implicit Laplacian of enhanced edge (ILEE), to accurately identify and analyze the biological status of the cytoskeleton from confocal image samples. This method significantly improves the accuracy, stability, and robustness of cytoskeleton segmentation, solves other technical hindrances, and enables abundant information to be extracted from images for biological interpretation (see Chapter 2). The ILEE algorithm will further help me to explore the phenotypes of actin architecture in response to immune signaling, which was not previously available due to the lack of the toolbox. Also, the ILEE has been packaged as a library released publicly to benefit the community with a powerful cytoskeleton analysis platform.For the second project of my total research, I focused on the immune function of the actin cytoskeleton in the nucleus. Previously, some Arabidopsis actin depolymerization factors were reported to genetically contribute to plant immunity by unknown mechanism(s), and my story began with a novel activity identified among Arabidopsis actin depolymerization factors – to interact with WRKYs, the stress-responsive transcription factors. During my research, I proved that certain ADFs can form a complex with WRKYs that binds to targeted promoters, hence regulating the activity of WRKYs and playing a positive role in the immune response. The knowledge obtained through this study, in combination with previous research (Lu et al., 2020; Porter et al., 2012a) of my lab, can be summarized into a biological model, in which ADF mediates a nuclear-cytoplasmic immune regulation that systemically facilitates both cytoskeleton dynamics and pro-immune transcriptome reprogramming. In general, this study reveals a novel yet general pattern of cytoskeleton mediated transcriptional regulation, as ADF and perhaps other components of the actin cytoskeleton can shuttle between the cytoplasm and nucleus to form a network with a higher level of complexity. As a potential broader impact, the application range of this model includes but is not necessarily limited to plant immunity.
Show less
- Title
- Structural connectivity of an interoception network in schizophrenia
- Creator
- Yao, Beier
- Date
- 2022
- Collection
- Electronic Theses & Dissertations
- Description
-
Interoception refers to the processing, integration, and interpretation of bodily signals by the brain. Interoception is key to not only basic survival, but also many cognitive processes, especially motivational and affective functioning. There is emerging evidence suggesting altered interoception in schizophrenia, but its neural underpinning has not been examined. The current study aims to investigate the structural connectivity of a putative interoception network in schizophrenia, and its...
Show moreInteroception refers to the processing, integration, and interpretation of bodily signals by the brain. Interoception is key to not only basic survival, but also many cognitive processes, especially motivational and affective functioning. There is emerging evidence suggesting altered interoception in schizophrenia, but its neural underpinning has not been examined. The current study aims to investigate the structural connectivity of a putative interoception network in schizophrenia, and its relationship with affective functioning and clinical symptoms. Thirty-five participants with schizophrenia (SZ) and 36 healthy control participants (HC) underwent diffusion tensor imaging (DTI) and performed tasks measuring emotional functioning. Probabilistic tractography was used to identify white matter tracts connecting the key hubs forming the interoception network (i.e., rostral and caudal anterior cingulate cortex, ventral anterior insula, dorsal mid and posterior insula, and amygdala). Microstructural integrity of these tracts was compared across groups and correlated with measures of emotional functioning and symptom severity. I found that SZ exhibited altered structural connectivity in the putative interoception network, compared to HC. The structural connectivity of the network was correlated with emotion recognition in HC, supporting a link between the interoception network and emotional functioning. However, this correlation was much weaker in SZ, suggesting less reliance on this network. I did not find a correlation between the structural connectivity and clinical symptoms in SZ. These findings suggest that altered interoception may play a role in illness mechanisms of schizophrenia, especially in relation to emotional deficits.
Show less
- Title
- Sex and Individual Differences in Agonistic Behavior of Spotted Hyenas (Crocuta Crocuta) : Effects on Fitness and Dominance
- Creator
- McCormick, S. Kevin
- Date
- 2022
- Collection
- Electronic Theses & Dissertations
- Description
-
Agonistic behavior can be observed across all taxa arising from a common need to compete over limiting resources. Within species, individual variation of agonistic behavior can allow individuals to acquire and maintain limiting resources leading to higher reproductive success or fitness. However, what is often overlooked in studies of agonistic behavior is submissiveness, and how this aspect of agonistic behavior relates to aggressiveness. Further, historical studies of agonistic behavior...
Show moreAgonistic behavior can be observed across all taxa arising from a common need to compete over limiting resources. Within species, individual variation of agonistic behavior can allow individuals to acquire and maintain limiting resources leading to higher reproductive success or fitness. However, what is often overlooked in studies of agonistic behavior is submissiveness, and how this aspect of agonistic behavior relates to aggressiveness. Further, historical studies of agonistic behavior among social mammals are biased towards studies of male agonistic behavior, often ignoring aspects and effects of female agonistic behavior. Here, I address these knowledge gaps through a long-term study of a free living highly gregarious mammal, the spotted hyena (Crocuta crocuta). Spotted hyenas offer an excellent model system for studying variation in aggressive and submissive behavior within individuals and between sexes, as they live in complex societies formed around a female dominated, or matrilineal, hierarchy that is enforced through constant agonistic interactions. For this dissertation, I utilized 30 years’ worth of consistently recorded behavioral data collected by Dr. Kay E. Holekamp and her team from free living hyenas residing within the Masai Mara National Reserve, Keyna. Because this dissertation involved many collaborations with other scientists, I use “we” throughout this abstract to describe participation in each chapter. In Chapter 1, we describe sexually dimorphic traits within spotted hyenas that fit common mammalian patterns, as well as numerous traits that violate mammalian norms, including sex differences in agonistic behavior. In particular, adult female spotted hyenas are significantly more likely to emit unsolicited acts of aggression down the hierarchy than adult breeding males, and females do so significantly more ferociously, or intensely. For Chapter 2, we analyzed rates and intensities of unprovoked aggressive and submissive acts emitted by adult females to determine if these two behaviors were individually consistent, as well as testing the hypothesis that these two behaviors may represent separate traits within individuals. Here we found that the intensity at which females emit aggressive and submissive behaviors are consistent, and that these traits were not correlated within individuals. Further, both consistent aggressive intensity and submissive intensity were correlated to adult female fitness, such that individuals expressing high or low extremes of these behaviors had lower annual offspring survival. Then in Chapter 3, we assessed drivers of female dominance within spotted hyenas. Within this chapter we tested two hypotheses 1) that intrinsic sex differences in agonistic behavior drives female dominance and/or 2) social support facilitates female dominance in this species. Further, we assessed these hypotheses among juvenile age classes to determine if drivers of female dominance occurred prior to sexual maturity and subsequent male dispersal. We found that females are intrinsically more aggressive both as cubs and adults, and adult males more submissive whether provoked or not. Further, social support during agonistic encounters is more likely to occur when acting against a female than a male, and adult females can dominate males with or without support. In completion, my dissertation provides interesting insights to sexual and individual variation on agonistic behavior among a social mammal.
Show less
- Title
- Efficient Transfer Learning for Heterogeneous Machine Learning Domains
- Creator
- Zhu, Zhuangdi
- Date
- 2022
- Collection
- Electronic Theses & Dissertations
- Description
-
Recent advances in deep machine learning hinge on a large amount of labeled data. Such heavy dependence on supervision data impedes the broader application of deep learning in more practical scenarios, where data annotation and labeling can be expensive (e.g. high-frequency trading) or even dangerous (e.g. training autonomous-driving models.) Transfer Learning (TL), equivalently referred to as knowledge transfer, is an effective strategy to confront such challenges. TL, by its definition,...
Show moreRecent advances in deep machine learning hinge on a large amount of labeled data. Such heavy dependence on supervision data impedes the broader application of deep learning in more practical scenarios, where data annotation and labeling can be expensive (e.g. high-frequency trading) or even dangerous (e.g. training autonomous-driving models.) Transfer Learning (TL), equivalently referred to as knowledge transfer, is an effective strategy to confront such challenges. TL, by its definition, distills the external knowledge from relevant domains into the target learning domain, hence requiring fewer supervision resources than learning-from-scratch. TL is beneficial for learning tasks for which the supervision data is limited or even unavailable. It is also an essential property to realize Generalized Artificial Intelligence. In this thesis, we propose sample-efficient TL approaches using limited, sometimes unreliable resources. We take a deep look into the setting of Reinforcement Learning (RL) and Supervised Learning, and derive solutions for the two domains respectively. Especially, for RL, we focus on a problem setting called imitation learning, where the supervision from the environment is either non-available or scarcely provided, and the learning agent must transfer knowledge from exterior resources, such as demonstration examples of a previously trained expert, to learn a good policy. For supervised learning, we consider a distributed machine learning scheme called Federated Learning (FL), which is a more challenging scenario than traditional machine learning, since the training data is distributed and non-sharable during the learning process. Under this distributed setting, it is imperative to enable TL among distributed learning clients to reach a satisfiable generalization performance. We prove by both theoretical support and extensive experiments that our proposed algorithms can facilitate the machine learning process with knowledge transfer to achieve higher asymptotic performance, in a principled and more efficient manner than the prior arts.
Show less
- Title
- MACHINE LEARNING TOWARDS DATA WITH COMPLEX STRUCTURES
- Creator
- Su, Runze
- Date
- 2022
- Collection
- Electronic Theses & Dissertations
- Description
-
The development of sequential analysis provides a deeper understanding in the exploration of many different fields. In the application of sequential analysis, there are two main challenges: How to extract informative features from a high-dimensional noisy domain? How to model the interaction for the information flow from multiple domains? We explored the two core challenges in bio-informatics, sales forecasting and multimedia services. In biology field, a typical problem is the to evaluate...
Show moreThe development of sequential analysis provides a deeper understanding in the exploration of many different fields. In the application of sequential analysis, there are two main challenges: How to extract informative features from a high-dimensional noisy domain? How to model the interaction for the information flow from multiple domains? We explored the two core challenges in bio-informatics, sales forecasting and multimedia services. In biology field, a typical problem is the to evaluate the interaction mechanism between non-coding DNA sequences and transcription. We propose CANEE, a convolutional self-attention architecture to analyze the function of non-coding DNA sequences. Compared to other existing models, CANEE achieves a better performance in overall prediction of 919 regulatory functions with respect to receiver operating characteristics and has a significant improvement on some responses in precision recall curve with shorter training time. In sales forecasting field, we extract a unique customers’ microbehavior dependency structure from clickstream data based on a Word-to-Vector model. Then, we build a clickstream informed LSTM model to forecast the car sales over 30 days. Our model significantly outperforms the classic seasonal autoregressive integrated moving average model. Besides, we demonstrate that transfer knowledge among different car models can further improve the performance. Other applications for multi-domain sequences happens in multimedia service field, where we focus on the understanding of multiple domain modalities, we propose new principles for audio visual learning and introduce a new framework as well as its training algorithm to set sight of videos’ themes to facilitate AVC learning.
Show less
- Title
- ELEMENTARY TEACHER CANDIDATES’ CONNECTIONS BETWEEN MATHEMATICS AND LITERACY AND THE CONTEXTUAL FACTORS THAT ENCOURAGE CONNECTION-MAKING
- Creator
- Hawley, Lisa A.
- Date
- 2022
- Collection
- Electronic Theses & Dissertations
- Description
-
Elementary teacher candidates (TCs) must learn to teach many subject areas. Although some mathematics education researchers have framed elementary teachers’ knowledge as a deficit (i.e., lack of depth of mathematics knowledge), this dissertation considers elementary teachers’ broad knowledge as a strength. Many elementary teachers and TCs feel anxious about teaching mathematics, but more confident in teaching other subjects, such as literacy. By identifying similarities between the teaching...
Show moreElementary teacher candidates (TCs) must learn to teach many subject areas. Although some mathematics education researchers have framed elementary teachers’ knowledge as a deficit (i.e., lack of depth of mathematics knowledge), this dissertation considers elementary teachers’ broad knowledge as a strength. Many elementary teachers and TCs feel anxious about teaching mathematics, but more confident in teaching other subjects, such as literacy. By identifying similarities between the teaching and learning of two subjects, they can draw on their knowledge of teaching other subjects to teach mathematics in a conceptually oriented, inquiry-based way. This case study of a cohort of elementary TCs taking concurrent mathematics and literacy methods courses sought to learn more about their connection-making by asking two questions: (a) What connections between subject areas, if any, do elementary TCs enrolled in concurrent literacy and mathematics methods courses identify? and (b) How do the contexts in which they are learning to teach encourage or limit the opportunities to make connections across subject areas? To answer the first question, I developed a conceptual framework of types of connections between mathematics and literacy, based on the research literature. This framework includes integrated curriculum, language as a basis for learning, and similarities in teaching and learning. I generated data through participant observations of class sessions and focus group discussions and analyzed the types of connections the TCs made using my framework. They identified a variety of connections between mathematics and literacy, with the two most frequent categories being about the role of reading in learning mathematics and similarities in pedagogy. To analyze the conditions which supported their connection making, I conceptualized the two methods courses as separate, but overlapping, communities of practice, and the focus group discussions as boundary encounters between them (Wenger, 1998). The focus groups, as boundary encounters, enabled TCs to identify a larger number of boundary objects (i.e., connections), as well as make richer connections. This took place through two types of knowledge brokering: brainstorming to identify boundary objects, and collaborative brokering, in which multiple participants contributed knowledge from other courses or experiences to collectively make sense of similarities or differences across the two subjects. In addition, my participation in collaborative brokering during the second focus group discussion suggests that TCs need the support of a more experienced knowledge broker to support their connection-making in order to go beyond surface-level similarities. These findings suggest that, in order to make connections that would enhance their mathematics teaching, elementary TCs need intentionally created spaces and the support of an instructor who is familiar with the teaching and learning of more than one subject area. This has implications for the structure of elementary teacher preparation programs, as well as the background and/or professional development of mathematics teacher educators who work with elementary TCs.
Show less