Predictive modelling of student dropout risk: Practical insights from a South Korean distance university.

Distance education supports lifelong learning and empowers individuals in rapidly changing societal conditions, yet it encounters high dropout rates due to a range of individual and societal obstacles. This study addresses the challenge of creating a practical prediction model by analyzing extensive real-world time-point data from a well-established online university in Seoul. Covering 144,540 instances from 2018 to 2022, the study integrates diverse datasets to compare the accuracy of models based on longitudinal, semester-wise, and gender-specific datasets. The demographic, academic, and online metrics identified significant dropout indicators, including age (particularly when binned), residential area, specific occupations, GPA, and LMS log metrics, using a stepwise backward elimination process. The study revealed that, despite societal changes, recent data from the last four semesters can be effectively used for stable prediction training. Gender-based analysis showed different factors influencing dropout risk for males and females. The Light Gradient Boosting Machine (LGBM) algorithm excelled in prediction accuracy, with the ROC-AUC metric affirming its superiority. However, logistic regression also showed its competitive performance and offered in-depth interpretation. In South Korea's distinct educational setting, merging advanced algorithms like LGBM with the interpretive strength of logistic regression is key for effective student support strategies.

A safe and effective plant gene switch system for tissue-specific induction of gene expression in Arabidopsis thaliana and Brassica juncea.

The ability to regulate spatial and temporal expression of genes is a useful tool in biotechnology as well as studies of functional genomics. Such regulation can provide information concerning the function of a gene in a developmental context while avoiding potential harmful effects due to constitutive overexpression of the gene. A GUS gene construct that uses the ecdysone receptor-based chemically inducible system and several different tissue-specific promoters was introduced into the model plant Arabidopsis thaliana and into the crop plant Brassica juncea. Here we describe the results of studies showing that this system provides both temporal and spatial control of transgene expression, and confirm that this system is useful for tissue-specific and temporal induction of gene expression in A. thaliana and B. juncea.

Induced accumulation of cuticular waxes enhances drought tolerance in Arabidopsis by changes in development of stomata.

Cuticular waxes are involved in the regulation of the exchange of gases and water in plants and can impact tolerance to drought. However, the molecular mechanisms of the relationship between wax accumulation and drought tolerance are largely unknown. We applied the methoxyfenozide gene switching system to regulate expression of the WIN1/SHN1 gene (WAX INDUCER 1/SHINE1; At1G15360), a transcriptional activator, to regulate production of cuticular waxes and cutin and followed changes of gene expression, metabolites, and drought tolerance. Treatment with the inducer resulted in expression of the target gene and specific downstream genes, and gradually increased cuticular waxes. Induction of cuticular wax conferred tolerance to drought and recovery from drought, and was correlated with reduced numbers of stomata. Quantitative RT-PCR assays using RNAs from transgenic plants revealed that when expression of the WIN1/SHN1 gene was induced there was increased expression of genes involved in wax development, and reduced expression of selected genes, including SPCH (At5g53210); MUTE (At3g06120); and FAMA (At3g241400); and YODA (At1g63700), each of which is involved in stomatal development. These studies suggest that drought tolerance caused by the induction of WIN1/SHIN gene may be due to reduced numbers of stomata as well as to cuticular wax accumulation.

Controlled silencing of 4-coumarate:CoA ligase alters lignocellulose composition without affecting stem growth.

Many bioenergy feedstocks are not easily converted to fermentable substrates due to of high proportions of lignin, which impedes the degradation of cell wall polysaccharides to fermentable sugars. To reduce lignin levels during plant growth, we generated transgenic Arabidopsis plants that contain a gene that confers inducible silencing of both 4CL1 and 4CL2 genes; these genes play a compensatory role in normal development of Arabidopsis, including in mechanisms of stem growth. To alter lignocellulose composition at specific times in plant development, genes were silenced at bolting, immature stages (5-7 cm high), and intermediate stages (10-15 cm high). The stems of induced plants at all stages of development exhibited increased cellulose content and reduced amounts of total lignin when compared with non-induced stems. Furthermore, treating plants at advanced stages of development (the immature and intermediate stages) had little impact on plant growth and development while plants treated at the bolting stage exhibited modest abnormal development. Our results suggest that it is possible to alter lignocellulose composition in plants without negative effects on plant growth.

Functional analysis of the activation domain of RF2a, a rice transcription factor.

Rice transcription factor RF2a binds to the BoxII cis element of the promoter of rice tungro bacilliform virus and activates promoter expression. The acidic acid-rich domain of RF2a is a transcription activator and has been partially characterized (Dai et al., 2003). The RF2a acidic domain (A; amino acids 49-116) was fused with the synthetic zinc finger ZF-TF 2C7 and was co-introduced with a reporter gene into transgenic Arabidopsis plants. Expression of the reporter gene was increased up to seven times by the effector. In transient assays in tobacco BY-2 protoplasts, we identified a subdomain comprising amino acids 56-84 (A5) that was equally as effective as an activator as the entire acidic domain. A chemically inducible system was used to show determined that A and A5 domains are equally as effective in transcription activation as the well-characterized VP16 activation domain. Bioinformatics analyses revealed that the A5 domain is present only in b-ZIP transcription factors. In dicots, the A domain contains an insertion of four amino acids that is not present in monocot proteins. The A5 domain, and similar domains in other b-ZIP transcription factors, is predicted to form an anti-parallel beta sheet structure.

Transcriptome profiling of vertical stem segments provides insights into the genetic regulation of secondary growth in hybrid aspen trees.

In order to better understand the genetic regulation of secondary growth in hybrid aspen (Populus tremula L.xP. alba L.), we carried out a series of cDNA-amplified fragment length polymorphism (AFLP)-based transcriptome analyses in vertical stem segments that represent a gradient of developmental stages with regard to secondary growth. This approach allowed us to screen >80% of the transcriptome expressed in six samples and identify genes differentially expressed with the progress of secondary growth, in a tissue-specific manner. Of the 76,800 transcript-derived fragments (TDFs) analyzed, 271 TDFs were selected and sequenced based on their differential expression patterns. Many of the xylem-up-regulated genes were involved in cell wall and lignin biosynthesis, while the bark-up-regulated genes had diverse functional roles. About 25% of the xylem-up-regulated TDFs analyzed were involved in the phenylpropanoid biosynthesis pathway, which produces the cell wall polymer lignin and various wood extractives. In addition, many of the TDFs showing secondary xylem-specific expression were annotated as genes not previously reported in Populus, including novel cell death proteins, cytoskeleton-interacting proteins, transporters and putative transcription factors.

Plant body weight-induced secondary growth in Arabidopsis and its transcription phenotype revealed by whole-transcriptome profiling.

Wood is an important raw material and environmentally cost-effective renewable source of energy. However, the molecular biology of wood formation (i.e. secondary growth) is surprisingly understudied. A novel experimental system was employed to study the molecular regulation of secondary xylem formation in Arabidopsis. First, we demonstrate that the weight carried by the stem is a primary signal for the induction of cambium differentiation and the plant hormone, auxin, is a downstream carrier of the signal for this process. We used Arabidopsis whole-transcriptome (23 K) GeneChip analysis to examine gene expression profile changes in the inflorescent stems treated for wood formation by cultural manipulation or artificial weight application. Many of the genes up-regulated in wood-forming stems had auxin responsive cis-acting elements in their promoter region, indicating auxin-mediated regulation of secondary growth. We identified 700 genes that were differentially expressed during the transition from primary growth to secondary growth. More than 40% of the genes that were up-regulated (>5x) were associated with signal transduction and transcriptional regulation. Biological significance of these regulatory genes is discussed in light of the induction and development of secondary xylem.

Functional characterization of allantoinase genes from Arabidopsis and a nonureide-type legume black locust.

The availability of nitrogen is a limiting factor for plant growth in most soils. Allantoin and its degradation derivatives are a group of soil heterocyclic nitrogen compounds that play an essential role in the assimilation, metabolism, transport, and storage of nitrogen in plants. Allantoinase is a key enzyme for biogenesis and degradation of these ureide compounds. Here, we describe the isolation of two functional allantoinase genes, AtALN (Arabidopsis allantoinase) and RpALN (Robinia pseudoacacia allantoinase), from Arabidopsis and black locust (Robinia pseudoacacia). The proteins encoded by those genes were predicted to have a signal peptide for the secretory pathway, which is consistent with earlier biochemical work that localized allantoinase activity to microbodies and endoplasmic reticulum (Hanks et al., 1981). Their functions were confirmed by genetic complementation of a yeast mutant (dal1) deficient in allantoin hydrolysis. The absence of nitrogen in the medium increased the expression of the genes. In Arabidopsis, the addition of allantoin to the medium as a sole source of nitrogen resulted in the up-regulation of the AtALN gene. The black locust gene (RpALN) was differentially regulated in cotyledons, axis, and hypocotyls during seed germination and seedling growth, but was not expressed in root tissues. In the trunk wood of a mature black locust tree, the RpALN gene was highly expressed in the bark/cambial region, but had no detectable expression in the sapwood or sapwood-heartwood transition zone. In addition, the gene expression in the bark/cambial region was up-regulated in spring and fall when compared with summer, suggesting its involvement in nitrogen mobilization.

Seasonal changes in gene expression at the sapwood-heartwood transition zone of black locust (Robinia pseudoacacia) revealed by cDNA microarray analysis.

Heartwood is a determining factor of wood quality and understanding the biology of heartwood may allow us to control its formation. Heartwood formation is a form of senescence that is accompanied by a variety of metabolic alterations in ray parenchyma cells at the sapwood-heartwood transition zone. Although senescence has been studied at the molecular level with respect to primary growth, the cell maturation and death events occurring during heartwood formation have been difficult to study because of their location and timing. Analysis of global gene expression patterns during the transition from sapwood to heartwood may offer a powerful means of identifying the mechanisms controlling heartwood formation. Previously, we developed cDNA microarrays carrying 2567 unigenes derived from the bark/cambium region, sapwood and transition zone of a mature black locust tree. Here, we describe the use of these microarrays to characterize seasonal changes in the expression patterns of 1873 genes from the transition zone of mature black locust trees. When samples collected in summer and fall were compared, 569 genes showed differential expression patterns: 293 genes were up-regulated (> twofold) in summer (July 5) and 276 genes were up-regulated in fall (November 27). More than 50% of the secondary and hormone metabolism-related genes on the microarrays were up-regulated in summer. Twenty-nine out of 55 genes involved in signal transduction were differentially regulated, suggesting that the ray parenchyma cells located in the innermost part of the trunk wood react to seasonal changes. We established the expression patterns of 349 novel genes (previously unknown or no-hit), of which 154 were up-regulated in summer and 195 were up-regulated in the fall.

Novel gene expression profiles define the metabolic and physiological processes characteristic of wood and its extractive formation in a hardwood tree species, Robinia pseudoacacia.

Wood is of critical importance to humans as a primary feedstock for biofuel, fiber, solid wood products, and various natural compounds including pharmaceuticals. The trunk wood of most tree species has two distinctly different regions: sapwood and heartwood. In addition to the major constituents, wood contains extraneous chemicals that can be removed by extraction with various solvents. The composition and the content of the extractives vary depending on such factors as, species, growth conditions, and time of year when the tree is cut. Despite the great commercial and keen scientific interest, little is known about the tree-specific biology of the formation of heartwood and its extractives. In order to gain insight on the molecular regulations of heartwood and its extractive formation, we carried out global examination of gene expression profiles across the trunk wood of black locust (Robinia pseudoacacia L.) trees. Of the 2,915 expressed sequenced tags (ESTs) that were generated and analyzed in the current study, 55.3% showed no match to known sequences. Cluster analysis of the ESTs identified a total of 2278 unigene sets, which were used to construct cDNA microarrays. Microarray hybridization analyses were then performed to survey the changes in gene expression profiles of trunk wood. The gene expression profiles of wood formation differ according to the region of trunk wood sampled, with highly expressed genes defining the metabolic and physiological processes characteristic of each region. For example, the gene encoding sugar transport had the highest expression in the sapwood, while the structural genes for flavonoid biosynthesis were up-regulated in the sapwood-heartwood transition zone. This analysis also established the expression patterns of 341 previously unknown genes.

Genes expressed in the latex of Hevea brasiliensis.

Rubber (cis-1,4-polyisoprene), an important raw material for many industrial uses, is synthesized in the latex of Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg. We postulated that the genes uniquely or preferentially expressed in the latex may be important for rubber biosynthesis. We constructed cDNA libraries from the latex of H. brasiliensis to investigate the genes expressed in the latex by single-run partial sequencing of the cDNA clones. Sequence analyses identified 245 expressed sequence tags (ESTs), of which 57% showed homology to previously described sequences in public databases. About 16% of the database-matched ESTs encode rubber biosynthesis-related proteins such as rubber elongation factor (REF) and small rubber particle protein (SRPP). The second most frequent transcripts next to rubber biosynthesis-related genes were defense genes and protein metabolism-related genes (12.6% each). About 27% of the database-matched ESTs had sequence homology with genes of unknown function. Among the redundantly expressed genes, REF was the most frequently expressed (6.1%), followed by SRPP (3.7%) and HbLAR (2.9%). Northern blot analyses showed that ten (71%) of the 14 ESTs studied were expressed at a higher level in latex than in leaves.