Plant Molecular Biology and Biotechnology Laboratory, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Melbourne, VIC, Australia.
Department of Plant Breeding, Justus Liebig University, Giessen, Germany.
Plant Reprod. 2021 Sep;34(3):225-242. doi: 10.1007/s00497-021-00411-6. Epub 2021 May 21.
Intron retention is a stage-specific mechanism of functional attenuation of a subset of co-regulated, functionally related genes during early stages of pollen development. To improve our understanding of the gene regulatory mechanisms that drive developmental processes, we performed a genome-wide study of alternative splicing and isoform switching during five key stages of pollen development in field mustard, Brassica rapa. Surprisingly, for several hundred genes (12.3% of the genes analysed), isoform switching results in stage-specific expression of intron-retaining transcripts at the meiotic stage of pollen development. In such cases, we report temporally regulated switching between expression of a canonical, translatable isoform and an intron-retaining transcript that is predicted to produce a truncated and presumably inactive protein. The results suggest a new pervasive mechanism underlying modulation of protein levels in a plant developmental program. The effect is not based on gene expression induction but on the type of transcript produced. We conclude that intron retention is a stage-specific mechanism of functional attenuation of a subset of co-regulated, functionally related genes during meiosis, especially genes related to ribosome biogenesis, mRNA transport and nuclear envelope architecture. We also propose that stage-specific expression of a non-functional isoform of Brassica rapa BrSDG8, a non-redundant member of histone methyltransferase gene family, linked to alternative splicing regulation, may contribute to the intron retention observed.
内含子保留是一组受调控的、功能相关基因在花粉发育早期功能衰减的特定阶段的机制。为了更好地理解调控发育过程的基因调控机制，我们对芸薹属植物芥菜花粉发育的五个关键阶段的选择性剪接和异构体转换进行了全基因组研究。令人惊讶的是，对于几百个基因（分析的基因的 12.3%），异构体转换导致在花粉发育的减数分裂阶段特异性表达内含子保留的转录本。在这种情况下，我们报告了在经典的、可翻译的异构体和一个内含子保留的转录本之间表达的时间调节转换，该转录本预计会产生一个截断的、可能无活性的蛋白质。研究结果表明，在植物发育程序中，蛋白水平的调节存在一种新的普遍机制。这种效果不是基于基因表达的诱导，而是基于产生的转录本的类型。我们得出结论，内含子保留是减数分裂过程中一组受调控的、功能相关基因的功能衰减的特定阶段的机制，特别是与核糖体生物发生、mRNA 转运和核膜结构相关的基因。我们还提出，BrSDG8 这种非冗余的组蛋白甲基转移酶基因家族成员的非功能异构体在芥菜中的特异性表达，可能与观察到的内含子保留有关。
