State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou, 510642, China.
College of Life Sciences, South China Agricultural University, Guangzhou, 510642, China.
J Integr Plant Biol. 2021 Aug;63(8):1537-1554. doi: 10.1111/jipb.13138. Epub 2021 Jul 7.
Plants have a hierarchical circadian structure comprising multiple tissue-specific oscillators that operate at different speeds and regulate the expression of distinct sets of genes in different organs. However, the identity of the genes differentially regulated by the circadian clock in different organs, such as roots, and how their oscillations create functional specialization remain unclear. Here, we profiled the diurnal and circadian landscapes of the shoots and roots of Medicago truncatula and identified the conserved regulatory sequences contributing to transcriptome oscillations in each organ. We found that the light-dark cycles strongly affect the global transcriptome oscillation in roots, and many clock genes oscillate only in shoots. Moreover, many key genes involved in nitrogen fixation are regulated by circadian rhythms. Surprisingly, the root clock runs faster than the shoot clock, which is contrary to the hierarchical circadian structure showing a slow-paced root clock in both detached and intact Arabidopsis thaliana (L.) Heynh. roots. Our result provides important clues about the species-specific circadian regulatory mechanism, which is often overlooked, and possibly coordinates the timing between shoots and roots independent of the current prevailing model.
植物具有分层的昼夜节律结构，由多个组织特异性振荡器组成，这些振荡器以不同的速度运行，并在不同的器官中调节不同基因集的表达。然而，昼夜节律钟在不同器官（如根）中差异调节的基因的身份，以及它们的振荡如何创造功能特化仍然不清楚。在这里，我们对紫花苜蓿的茎和根的昼夜节律景观进行了分析，并鉴定了有助于每个器官转录组振荡的保守调控序列。我们发现，光暗循环强烈影响根的全局转录组振荡，并且许多生物钟基因仅在茎中振荡。此外，许多参与固氮的关键基因受到昼夜节律的调节。令人惊讶的是，根钟的运行速度快于茎钟，这与在拟南芥（L.）Heynh 的离体和完整根中表现出慢节奏根钟的分层昼夜节律结构相反。我们的结果提供了关于通常被忽视的物种特异性昼夜节律调节机制的重要线索，并且可能独立于当前流行的模型协调茎和根之间的时间。
