Computational Molecular Biology 2025, Vol.15, No.1, 38-52 http://bioscipublisher.com/index.php/cmb 46 7 Epigenetic Regulation in Rapeseed Development and Stress Response 7.1 DNA methylation and its impact on gene expression DNA methylation acts like a "gene switch" in rapeseed's adaptation to adverse conditions, with a very ingenious regulatory approach. When nitrogen deficiency occurs, rapeseed will reprogram gene expression by adjusting the methylation pattern (Hua et al., 2020)-just like labeling different genes as "enabled" or "disabled", especially those involved in nitrogen metabolism, thereby improving nitrogen utilization efficiency. Interestingly, when facing salt stress, this system plays new tricks, and the methylation markers are specifically adjusted for the transcription factors that regulate stress resistance. In fact, the effect of methylation is entirely dependent on the location-in some places, methylation activates genes, while in others it silenced them. This flexible regulation enables rapeseed to quickly respond to various environmental pressures without altering its DNA sequence, saving energy and being highly efficient. It can be regarded as an "intelligent regulation system" in the plant kingdom. 7.2 Histone modifications in transcriptional control When rapeseed responds to environmental stress, histones are like regulatory masters wearing various chemical "hats", and these modifications directly determine the on-off state of genes. Interestingly, the histone deacetylase HDA9 and the transcription factor WRKY53 are like a pair of rivals (Zheng et al., 2019), with the former "removing the label" from the latter, resulting in a decline in resilience. The phenomena found in soybeans (Song et al., 2012), such as H3K4 trimethylation and H3K9 acetylation, are also likely to play a similar role in rapeseed. In fact, these histone modifications are like precise tuning knobs-when methyl or acetyl groups are added, the chromatin structure undergoes subtle changes, thereby precisely regulating gene expression levels. This regulatory approach that does not alter the DNA sequence but can quickly respond to environmental changes demonstrates the survival wisdom formed by plants during their long-term evolution. 7.3 Small RNAs and transcriptional silencing mechanisms Those insignificant small RNAs (sRNAs) in rapeseed actually hold significant regulatory power. These little ones, including miRNA and siRNA, collectively "switch positions" when nitrogen is deficient-some adjust leaf development, some manage amino acid metabolism, and some specifically regulate hormone signals. Work together to help the plants get through the difficult times. Even more amazing is the ability of siRNA (Simon and Meyers, 2011), which can directly mark methylation on DNA or change histone modifications, just like a small conductor precisely controlling gene switches. In fact, this system is particularly adept at dealing with "junk DNA" in the genome, silencing these potentially dangerous regions by forming heterochromatin. These findings suggest that rapeseed's adaptation to the environment is not achieved through the individual efforts of a few star genes, but rather through a sophisticated regulatory network jointly constructed by "behind-the-scenes workers" such as sRNA, DNA methylation, and histone modification. 8 Case Study: Transcriptional Response to Drought Stress in Rapeseed 8.1 Overview of drought-stress challenges in rapeseed cultivation When rapeseed encounters drought, the water in the cells is the first to be affected-just like a sudden water cut-off. At this time, the plant will activate the emergency plan: on the one hand, it will vigorously accumulate "water-retaining agents" such as proline; on the other hand, it will increase the level of antioxidant enzymes to eliminate free radical damage. Interestingly, different varieties have different coping strategies-some are busy adjusting the opening and closing of stomata, while others focus on changing the root structure. From a molecular perspective, drought can cause a major reshuffle of the entire transcriptome (Zhang et al., 2019), the expression of thousands of genes has changed, as if rewriting the survival program. These findings indicate that the drought resistance of rapeseed does not rely on a single mechanism, but rather maintains its life activities through a comprehensive strategy that involves multiple approaches. 8.2 Key transcriptional changes observed under drought When drought strikes, the genetic activity within rape plants undergoes a complete transformation. Genome-wide scanning revealed that the differences in gene expression between drought-tolerant varieties and sensitive varieties were very significant; In 2020, tens of thousands of mrnas and lncrnas were either abnormally active or simply on
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