Root PRR7 improves the accuracy of the shoot circadian clock through nutrient transport

The circadian clock allows plants to anticipate and adapt to periodic environmental changes. Organ- and tissue-specific properties of the circadian clock and shoot-to-root circadian signaling have been reported. While this long-distance signaling is thought to coordinate physiological functions across tissues, little is known about the feedback regulation of the root clock on the shoot clock in the hierarchical circadian network. Here, we show that the plant circadian clock conveys circadian information between shoots and roots through sucrose and K⁺. We also demonstrate that K+ transport from roots suppresses the variance of period length in shoots and then improves the accuracy of the shoot circadian clock. Sucrose measurements and qPCR showed that root sucrose accumulation was regulated by the circadian clock. Furthermore, root circadian clock genes, including PSEUDO-RESPONSE REGULATOR7 (PRR7), were regulated by sucrose, suggesting the involvement of sucrose from the shoot in the regulation of root clock gene expression. Therefore, we performed time-series measurements of xylem sap and micrografting experiments using prr7 mutants and showed that root PRR7 regulates K⁺ transport and suppresses variance of period length in the shoot. Our modeling analysis supports the idea that root-to-shoot signaling contributes to the precision of the shoot circadian clock. We performed micrografting experiments that illustrated how root PRR7 plays key roles in maintaining the accuracy of shoot circadian rhythms. We thus present a novel directional signaling pathway for circadian information from roots to shoots and propose that plants modulate physiological events in a timely manner through various timekeeping mechanisms

A guiding role of the Arabidopsis circadian clock in cell differentiation revealed by time-series single-cell RNA sequencing

Circadian rhythms and progression of cell differentiation are closely coupled in multicellular organisms. However, whether establishment of circadian rhythms regulates cell differentiation or vice versa has not been elucidated due to technical limitations. Here, we exploit high cell fate plasticity of plant cells to perform single-cell RNA sequencing during the entire process of cell differentiation. By analyzing reconstructed actual time series of the differentiation processes at single-cell resolution using a method we developed (PeakMatch), we find that the expression profile of clock genes is changed prior to cell differentiation, including induction of the clock gene LUX ARRYTHMO (LUX). ChIP sequencing analysis reveals that LUX induction in early differentiating cells directly targets genes involved in cell-cycle progression to regulate cell differentiation. Taken together, these results not only reveal a guiding role of the plant circadian clock in cell differentiation but also provide an approach for time-series analysis at single-cell resolution

多職種連携と患者特性に配慮したケアを行った高度肥満症の一例

A ４８-year-old man who weighed ２１６ kg was significantly overweight with a body mass index （BMI）of ７５．６kg/m２, and was unable to walk due to disuse syndrome. Because of the psychological and social problems in the background, a psychological examination was performed and the staff took time to build a trusting relationship with the patient, taking into account his characteristics. With diet and rehabilitation, he was able to lose weight to １２４kg and BMI ４３．９kg/m２ over ６００ days, and was able to walk with assistive devices and defecate by himself. The patient was discharged from our hospital after a series of multidisciplinary meetings with medical, nursing, welfare, and governmental agencies to create an environment for home recuperation. The reasons for the improvement to enable him to be discharged from the hospital were due to the multi-disciplinary meetings among the staff inside and outside the hospital, information sharing and advanced coordination, and smooth communication with the patient by taking into account his characteristics from a psychological standpoint

Photoperiod sensitivity of the Arabidopsis circadian clock is tissue-specific.

Tissue-specific functions of the circadian clock in Arabidopsis have recently been revealed. The vasculature clock shows distinctive gene expression profiles compared to the clock in other tissues under light-dark cycles. However, it has not yet been established whether the vasculature clock also shows unique gene expression patterns that correlate with temperature cycles, another important environmental cue. Here, we detected diel phase of TIMING OF CAB EXPRESSION 1 (TOC1) expression in the vasculature and whole leaf under long-day light-dark cycles and temperature cycles. We found that the vasculature clock had advanced TOC1 phase under light-dark cycles but not under temperature cycles, suggesting that the vasculature clock has lower sensitivity against temperature signals. Furthermore, the phase advancement of TOC1 was seen only under long-day condition but not under short-day condition. These results support our previous conclusion that the circadian clock in vasculature preferentially senses photoperiodic signals

Circadian clock during plant development

The original version of this article was revised due to a retrospective open access order.An erratum to this article is available online at https://doi.org/10.1007/s10265-018-1015-z. (Inoue, K., Araki, T. & Endo, M. J Plant Res (2018) 131: 571.)Plants have endogenous biological clocks that allow organisms to anticipate and prepare for daily and seasonal environmental changes and increase their fitness in changing environments. The circadian clock in plants, as in animals and insects, mainly consists of multiple interlocking transcriptional/translational feedback loops. The circadian clock can be entrained by environmental cues such as light, temperature and nutrient status to synchronize internal biological rhythms with surrounding environments. Output pathways link the circadian oscillator to various physiological, developmental, and reproductive processes for adjusting the timing of these biological processes to an appropriate time of day or a suitable season. Recent genomic studies have demonstrated that polymorphism in circadian clock genes may contribute to local adaptations over a wide range of latitudes in many plant species. In the present review, we summarize the circadian regulation of biological processes throughout the life cycle of plants, and describe the contribution of the circadian clock to local adaptation

Decentralized circadian clocks process thermal and photoperiodic cues in specific tissues

植物の体内時計が日の長さと温度の情報を異なる組織で処理していることを発見. 京都大学プレスリリース. 2015-11-04.The circadian clock increases organisms' fitness by regulating physiological responses1. In mammals, the circadian clock in the suprachiasmatic nucleus (SCN) governs daily behavioural rhythms2. Similarly, in Arabidopsis, tissue-specific circadian clock functions have emerged, and the importance of the vasculature clock for photoperiodic flowering has been demonstrated. However, it remains unclear if the vasculature clock regulates the majority of physiological responses, like the SCN in mammals, and if other environmental signals are also processed by the vasculature clock. Here, we studied the involvement of tissue-specific circadian clock regulation of flowering and cell elongation under different photoperiods and temperatures. We found that the circadian clock in vascular phloem companion cells is essential for photoperiodic flowering regulation; by contrast, the epidermis has a crucial impact on ambient temperature-dependent cell elongation. Thus, there are clear assignments of roles among circadian clocks in each tissue. Our results reveal that, unlike the more centralized circadian clock in mammals, the plant circadian clock is decentralized, where each tissue specifically processes individual environmental cues and regulates individual physiological responses. Our new conceptual framework will be a starting point for deciphering circadian clock functions in each tissue, which will lead to a better understanding of how circadian clock processing of environmental signals may be affected by ongoing climate change