Insights into Land Plant Evolution Garnered from the Marchantia polymorpha Genome.

The evolution of land flora transformed the terrestrial environment. Land plants evolved from an ancestral charophycean alga from which they inherited developmental, biochemical, and cell biological attributes. Additional biochemical and physiological adaptations to land, and a life cycle with an alternation between multicellular haploid and diploid generations that facilitated efficient dispersal of desiccation tolerant spores, evolved in the ancestral land plant. We analyzed the genome of the liverwort Marchantia polymorpha, a member of a basal land plant lineage. Relative to charophycean algae, land plant genomes are characterized by genes encoding novel biochemical pathways, new phytohormone signaling pathways (notably auxin), expanded repertoires of signaling pathways, and increased diversity in some transcription factor families. Compared with other sequenced land plants, M. polymorpha exhibits low genetic redundancy in most regulatory pathways, with this portion of its genome resembling that predicted for the ancestral land plant. PAPERCLIP.

The Balance of CD8-Positive T Cells and PD-L1 Expression in the Myocardium Predicts Prognosis in Lymphocytic Fulminant Myocarditis.

INTRODUCTION: The clinical significance and prognostic value of T cell involvement and programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) have not been established in lymphocytic fulminant myocarditis (FM). We investigated the prognostic impact of the number of CD4+, CD8+, FoxP3+, and PD-1+ T cells, as well as PD-L1 expression, in cardiomyocytes in lymphocytic FM. METHODS: This is a single-center observational cohort study. Myocardial tissue was obtained from 16 consecutive patients at lymphocytic FM onset. The median follow-up was 140 days. Cardiac events were defined as a composite of cardiac death and left ventricular-assist device implantation. CD4, CD8, FoxP3, PD-1, and PD-L1 immunostaining were performed on myocardial specimens. RESULTS: The median age of the patients was 52 years (seven men and nine women). There was no significant difference in the number of CD4+ cells. The number of CD8+ cells and the CD8+/CD4+ T cell ratio were higher in the cardiac event group (Event+) than in the group without cardiac events (Event-) (p = 0.048 and p = 0.022, respectively). The number of FoxP3+ T cells was higher in the Event+ group (p = 0.049). Although there was no difference in the number of PD-1+ cells, cardiomyocyte PD-L1 expression was higher in the Event+ group (p = 0.112). Event-free survival was worse in the group with a high CD8+ cell count (p = 0.012) and high PD-L1 expression (p = 0.049). When divided into three groups based on the number of CD8+ cells and PD-L1 expression (CD8highPD-L1high [n = 8], CD8lowPD-L1high [n = 1], and CD8lowPD-L1low [n = 7]), the CD8highPD-L1high group demonstrated the worst event-free survival, while the CD8lowPD-L1high group had a favorable prognosis without cardiac events (p = 0.041). CONCLUSION: High myocardial expression of CD8+ T cells and PD-L1 may predict a poor prognosis in lymphocytic FM.

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.

Relationship between the volume of cases and in-hospital mortality in patients with cardiogenic shock receiving short-term mechanical circulatory support.

BACKGROUND: We examined the relationship between annual case volume at each hospital and outcome in cardiogenic shock (CS) patients receiving mechanical circulatory support (MCS) devices. METHODS: This cross-sectional study used the Japanese nationwide database to identify patients receiving short-term MCS for CS between April 2012 and March 2020. Of 65,837 patients, 3 subcohorts were created; the intra-aortic balloon pump (IABP) alone (n = 48,643), the extracorporeal membrane oxygenation (ECMO) (n = 16,871), and the Impella cohorts (n = 696). RESULTS: The median annual case volume was 13.5 (7.4-22.1) in the IABP alone cohort, 6.4 (3.4-11.0) in the ECMO cohort, and 7.5 (4.0-10.7) in the Impella cohort. The highest quintile for the volume of cases in the IABP alone and ECMO had the lowest in-hospital mortality (IABP alone, 25.1% in quintile 1 vs 15.2% in quintile 5; ECMO, 73.7% in quintile 1 in 67.4% in quintile 5). Adjusted ORs for in-hospital mortality decreased as case volume increased (IABP alone, 0.63 [0.58-0.68] in quintile 5; ECMO, 0.73 [0.65-0.82] in quintile 5, with the lowest quintile as reference) but did not decrease significantly in the Impella (0.90 [0.58-1.39] in tertile 3, with the lowest tertile as reference). In the continuous models with the case volume as a continuous variable, adjusted ORs for in-hospital mortality decreased to 28 IABP cases/year and 12 ECMO cases/year. They did not decrease or became almost flat above that. CONCLUSIONS: Higher volumes of IABP and ECMO are associated with a lower mortality. There is an upper limit to the decline. Centralizing patients with refractory CS in a particular hospital might improve patient outcomes in each region.

Increased risk of purge system malfunction after Impella 5.0 replacement: a case series.

The Impella 5.0 is an axial-flow percutaneous ventricular assist device used in patients with cardiogenic shock. Although the recommended period of use is 10 days or less, weaning can be delayed because of ongoing hemodynamic instability. In clinical practice, this device sometimes malfunctions during long-term management with heparin and must be replaced; however, the relationship between the duration of support with the initial and replacement Impella 5.0 and the changes in value of the purge system has not been fully elucidated. From July 2018 to May 2021, Impella 5.0 was implanted and used for more than 10 days in 11 patients at our institution. Four patients required Impella replacement because of device malfunction and the second Impella had purge system malfunction in all cases. The second Impella was used for a significantly shorter time than the first Impella (p = 0016). We calculated the ratio of purge pressure to purge flow rate and found that the ratio exceeded 50 mm Hg/mL/h in all cases with purge system malfunction. In conclusion, it is important to construct a treatment strategy considering the duration of use, because the risk of purge system malfunction is high after replaced Impella 5.0.

[Pediatric Neuroemergency].

The goal of initial management of any pediatric emergency patient is to rapidly assess and resuscitate the condition and provide radical therapeutic intervention while determining treatment priorities. While resuscitation is performed safely and reliably, the patient's condition should be reevaluated on an ongoing basis to determine the efficacy of the treatment. This systematic and logical approach is necessary. If the physician is unfamiliar with the examination of infants, it is most ideal to request pediatrician prior to transport, and to collaborate in the evaluation of the pediatric patient's condition and the securing of intravenous routes. In case of traumatic patient, it is advisable to notify the relevant departments in advance, such as the transfusion department and operating room. The patient's age and weight should be confirmed and accommodated. The most commonly observed symptoms in the initial treatment of children are seizures and disturbance of consciousness. Since children are particularly prone to seizures and since they can appear as a symptom of various diseases, it is necessary to differentiate the primary disease. The severity of the disturbance of consciousness depends on the types and duration of the seizures and the degree of status epilepticus making them highly urgent. Collaborate with the pediatrician because of the wide variety of differential diseases. The response to seizures and recognition of child abuse will be summarized at the end of this section.

Clinical Effect of Pulmonary Artery Diameter/Ascending Aorta Diameter Ratio on Left Ventricular Reverse Remodeling in Patients With Dilated Cardiomyopathy.

BACKGROUND: Many patients with dilated cardiomyopathy (DCM) progress to heart failure (HF), although some demonstrate left ventricular (LV) reverse remodeling (LVRR), which is associated with better outcomes. The pulmonary artery diameter (PAD) to ascending aortic diameter (AoD) ratio has been used as a prognostic predictor in patients with HF, although this tool's usefulness in predicting LVRR remains unknown.Methods and Results: Data from a prospective observational study of 211 patients diagnosed in 2000-2020 with DCM were retrospectively analyzed. Sixty-nine patients with New York Heart Association class I or II HF were included. LVRR was observed in 23 patients (33.3%). The mean LV ejection fraction (29%) and LV end-diastolic dimension (64.5 mm) were similar in patients with and without LVRR. The PAD/AoD ratio was significantly lower in patients with LVRR than those without (81.4% vs. 92.4%, respectively; P=0.003). The optimal PAD/AoD cut-off value for detecting LVRR was 0.9 according to the receiver operating characteristic curve analysis. Multivariate analysis identified a PAD/AoD ratio ≥0.9 as an independent predictor of presence/absence of LVRR. Cardiac events were significantly more common in patients with a PAD/AoD ratio ≥0.9 than those with a ratio <0.9, after a median follow up of 2.5 years (log-rank, P=0.007). CONCLUSIONS: The PAD/AoD ratio can predict LVRR in patients with DCM.

Prognostic value of malnutrition evaluated using the Global Leadership Initiative on Malnutrition criteria and its association with psoas muscle volume in non-ischemic dilated cardiomyopathy.

Heart failure (HF) is a systemic inflammatory disease that causes hypotrophy and skeletal muscle loss. The Global Leadership Initiative on Malnutrition (GLIM) criteria have been developed as a novel evaluation index for malnutrition, with reported usefulness in HF caused by ischemic heart disease. However, reports on the usefulness of malnutrition evaluated by the GLIM criteria in non-ischemic dilated cardiomyopathy (NIDCM) and its relationship with psoas muscle volume are lacking. We investigated the prognostic value of malnutrition evaluated using the GLIM criteria and its association with psoas muscle volume in patients with NIDCM. We enrolled 139 consecutive patients with NIDCM between December 2000 and June 2020. Malnutrition was evaluated using the GLIM criteria on admission. The median follow-up period was 4.7 years. Cardiac events were defined as a composite of cardiac death, hospitalization for worsening HF, and lethal arrhythmia. Furthermore, we measured the psoas muscle volume using computed tomography volumetry in 48 patients. At baseline, the median age was 50 years, and 132 patients (95.0%) had New York Heart Association functional class I or II HF. The median psoas muscle volume was 460.8 cm3. A total of 26 patients (18.7%) were malnourished according to the GLIM criteria. The Kaplan-Meier survival analysis showed that malnourished patients had more cardiac events than non-malnourished patients (log-rank, P < 0.001). The multivariate Cox proportional hazards regression analysis revealed that GLIM criteria-based malnutrition was an independent determinant of cardiac events (hazard ratio, 2.065; 95% confidence interval, 1.166-3.656; P = 0.014). Psoas muscle volume, which was assessed in a total of 48 patients, was lower in malnourished than in non-malnourished patients (median, 369.0 vs. 502.3 cm3; P = 0.035) and correlated with body mass index (r = 0.441; P = 0.002). Nutritional screening using the GLIM criteria may be useful in predicting future cardiac events in patients with NIDCM, reflecting a potential relationship between malnutrition and a low psoas muscle volume.

Splenic size as an indicator of hemodynamics and prognosis in patients with heart failure.

The spleen is an important immune organ that releases erythrocytes and monocytes and destroys aged platelets. It also reserves 20-30% of the total blood volume, and its size decreases in hypovolemic shock. However, the clinical significance of splenic size in patients with heart failure (HF) remains unclear. We retrospectively analyzed the data of 206 patients with clinically stable HF gathered between January 2001 and August 2020 and recorded in a single-center registry. All patients underwent right heart catheterization and computed tomography (CT). Splenic size was measured using CT volumetry. The primary outcomes were composite cardiac events occurring for the first time during follow-up, namely, cardiac death and hospitalization for worsening HF. The median splenic volume and splenic volume index (SVI) were 118.0 mL and 68.9 mL/m2, respectively. SVI was positively correlated with cardiac output (r = 0.269, P < 0.001) and stroke volume (r = 0.228, P = 0.002), and negatively correlated with systemic vascular resistance (r = - 0.302, P < 0.001). Seventy cardiac events occurred, and the optimal receiver operating characteristic curve SVI cutoff value for predicting cardiac events was 68.9 mL/m2. The median blood adrenaline concentration was higher in the low-SVI group than the high-SVI group (0.039 ng/mL vs. 0.026 ng/mL, respectively; P = 0.004), and the low-SVI group experienced more cardiac events (log-rank test, P < 0.001). Multivariate Cox proportional hazards regression revealed that a low SVI was an independent predictor of cardiac events, even when adjusted for the validated HF risk score, blood-brain natriuretic peptide concentration, blood catecholamine concentrations, and hemodynamic parameters. Splenic size reflects hemodynamics, including systemic circulating blood volume status and sympathetic nerve activity, and is associated with HF prognosis.

ASSOCIATION OF FLOW SIGNALS WITHIN POLYPS ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY WITH TREATMENT RESPONSES AFTER COMBINATION THERAPY FOR POLYPOIDAL CHOROIDAL VASCULOPATHY.

PURPOSE: To evaluate the changes of blood circulation within the polypoidal lesions by OCT angiography in eyes with polypoidal choroidal vasculopathy after combination therapy with aflibercept and photodynamic therapy. METHODS: A total of 46 eyes from 46 patients who underwent the combination therapy for polypoidal choroidal vasculopathy were followed for more than 6 months. OCT angiography, covering an area 6 mm2 × 6 mm2 including the macula, were performed at baseline, 2 weeks, and 3 months and 6 months post-treatment. RESULTS: The subretinal fluid resolved within 3 months after treatment in 44 eyes (95.7%), and 27 eyes (58.7%) showed no recurrence, with no additional treatment. Seventeen eyes (37.0%) showed recurrence, and two eyes (4.3%) showed poor response. On OCT angiography at 2 weeks after treatment, flow signals were detected in 3 of 27 eyes (11.1%) without recurrence and in 8 of 19 eyes (42.1%) with recurrence or poor responses. A detectable flow signal at 2 weeks was significantly associated with recurrence or poor response (P = 0.032). CONCLUSION: Persistent flow signals within polyps on OCT angiography at 2 weeks after combination therapy suggest less effectiveness of the initial treatment.

Abusive head trauma in Japan.

PURPOSE: Abusive head trauma (AHT) is a serious cause of morbidity and mortality in the pediatric population, especially in young infants. This review of the literature aimed to understand the characteristics of AHT in Japan. METHODS: PubMed and the Japanese database Ichuushi were searched to understand the differences in AHT between Japan and other countries. RESULTS: Shaking was identified as an uncommon cause of injury, while mothers were the most common perpetrator of pediatric AHT in Japan. Although uncommon in other countries, infantile subdural hematoma caused by an accidental slight head injury was reported in Japan. CONCLUSION: As in other countries, AHT is a major condition which pediatric neurosurgeons face in Japan. The mechanisms of injury and perpetrators of AHT seemed to differ slightly between western countries and Japan. Additionally, non-accidental infantile acute subdural hematoma was reported mainly in Japan. Therefore, further care and fair judgment is necessary when investigating child abuse in Japan.

[Craniotomy/ICP Sensor Insertion].

Traumatic injuries in infants tend to be concentrated in the head due to the large volume ratio of the head to the trunk, and the injury mechanisms change from passive(e.g., crashes and falls from a certain height due to caregiver negligence, or child abuse)to automatic(e.g., playground equipment and bicycle accidents, crashes and falls from heights)as the child grows and develops. Subsequently, as mobility increases, injuries from traffic accidents, sports-related trauma, and self-inflicted injuries increase. In addition, there are many cases that require urgent surgical treatment for forms of injury unique to the pediatric age, such as epidural hematoma, depressed fractures and penetrating traumatic brain injury. Since pediatric head injury is a broad category encompassing all of these changes, it is necessary to appropriately address the anatomical and physiological changes in the central nervous system, and detailed treatment that takes into account the individual background can lead to a better functional prognosis. This article describes craniotomies for head injury seen in pediatric age other than acute subdural hematoma(acute epidural hematoma, open depressed fracture, and penetrating traumatic brain injury)and also describes the technique of intracranial pressure sensor insertion, which is key to intensive care for intracranial hypertension.

[Abusive Head Trauma].

Abusive head trauma(AHT) is a leading cause of severe traumatic brain injury in children under 2 years old. Patients with AHT present with various clinical features, including acute subdural hematoma, retinal hemorrhage, and extensive hemispheric hypodensity, which has recently been reproduced in a basic experimental model. Despite multidisciplinary treatment, the outcome is poor, and neurological sequelae often remain. However, functional recovery seems possible with aggressive rehabilitation. The medical rationale for the diagnosis of AHT has a significant impact on the judicial decision-making process to determine evidence of child abuse, enabling collaboration with the police, prosecutors, and other investigative agencies, including lawyers. In Japan, infantile acute subdural hematoma(hematoma type I)is a clinical form of hematoma that often occurs after 6-10 months, when the child is able to walk. It is accompanied by backward fall, sudden loss of consciousness, pallor, spastic paralysis of the extremities, and retinal hemorrhage. A nationwide survey of infant acute subdural hematoma due to minor injury is currently being planned, and it is hoped that this would be comprehensive in Japan. Medical personnel involved in neurosurgical emergencies have an important responsibility as a safety network for pediatric care and are expected to play a central role in the diagnosis of AHT through collaboration with many specialized departments.

Oscillator networks with tissue-specific circadian clocks in plants.

Many organisms rely on circadian clocks to synchronize their biological processes with the 24-h rotation of the earth. In mammals, the circadian clock consists of a central clock in the suprachiasmatic nucleus and peripheral clocks in other tissues. The central clock is tightly coupled to synchronize rhythmicity and can organize peripheral clocks through neural and hormonal signals. In contrast to mammals, it has long been assumed that the circadian clocks in each plant cell is able to be entrained by external light, and they are only weakly coupled to each other. Recently, however, several reports have demonstrated that plants have unique oscillator networks with tissue-specific circadian clocks. Here, we introduce our current view regarding tissue-specific properties and oscillator networks of plant circadian clocks. Accumulating evidence suggests that plants have multiple oscillators, which show distinct properties and reside in different tissues. A direct tissue-isolation technique and micrografting have clearly demonstrated that plants have hierarchical oscillator networks consisting of multiple tissue-specific clocks.

Time-Series Single-Cell RNA-Seq Data Reveal Auxin Fluctuation during Endocycle.

Appropriate cell cycle regulation is crucial for achieving coordinated development and cell differentiation in multicellular organisms. In Arabidopsis, endoreduplication is often observed in terminally differentiated cells and several reports have shown its molecular mechanisms. Auxin is a key factor for the mode transition from mitotic cell cycle to endocycle; however, it remains unclear if and how auxin maintains the endocycle mode. In this study, we reanalyzed root single-cell transcriptome data and reconstructed cell cycle trajectories of the mitotic cell cycle and endocycle. With progression of the endocycle, genes involved in auxin synthesis, influx and efflux were induced at the specific cell phase, suggesting that auxin concentration fluctuated dynamically. Such induction of auxin-related genes was not observed in the mitotic cell cycle, suggesting that the auxin fluctuation plays some roles in maintaining the endocycle stage. In addition, the expression level of CYCB1;1, which is required for cell division in the M phase, coincided with the expected amount of auxin and cell division. Our analysis also provided a set of genes expressed in specific phases of the cell cycle. Taking these findings together, reconstruction of single-cell transcriptome data enables us to identify properties of the cell cycle more accurately.

Tissue-specific clocks in Arabidopsis show asymmetric coupling.

Many organisms rely on a circadian clock system to adapt to daily and seasonal environmental changes. The mammalian circadian clock consists of a central clock in the suprachiasmatic nucleus that has tightly coupled neurons and synchronizes other clocks in peripheral tissues. Plants also have a circadian clock, but plant circadian clock function has long been assumed to be uncoupled. Only a few studies have been able to show weak, local coupling among cells. Here, by implementing two novel techniques, we have performed a comprehensive tissue-specific analysis of leaf tissues, and show that the vasculature and mesophyll clocks asymmetrically regulate each other in Arabidopsis. The circadian clock in the vasculature has characteristics distinct from other tissues, cycles robustly without environmental cues, and affects circadian clock regulation in other tissues. Furthermore, we found that vasculature-enriched genes that are rhythmically expressed are preferentially expressed in the evening, whereas rhythmic mesophyll-enriched genes tend to be expressed in the morning. Our results set the stage for a deeper understanding of how the vasculature circadian clock in plants regulates key physiological responses such as flowering time.

Reproductive Induction is a Far-Red High Irradiance Response that is Mediated by Phytochrome and PHYTOCHROME INTERACTING FACTOR in Marchantia polymorpha.

Land plants have evolved a series of photoreceptors to precisely perceive environmental information. Among these, phytochromes are the sole photoreceptors for red light (R) and far-red light (FR), and play pivotal roles in modulating various developmental processes. Most extant land plants possess multiple phytochromes that probably evolved from a single phytochrome in the common ancestor of land plants. However, the ancestral phytochrome signaling mechanism remains unknown due to a paucity of knowledge regarding phytochrome functions in basal land plants. It has recently been reported that Mpphy, a single phytochrome in the liverwort Marchantia polymorpha, regulates typical photoreversible responses collectively classified as low fluence response (LFR). Here, we show that Mpphy also regulates the gametangiophore formation analogous to the mode of action of the far-red high irradiance response (FR-HIR) in angiosperms. Our phenotypic analyses using mutant plants obtained by CRISPR/Cas9-based genome editing revealed that MpFHY1, an ortholog of FAR-RED ELONGATED HYPOCOTYL1, as well as Mpphy is critical for the FR-HIR signaling in M. polymorpha. In addition, knockout of MpPIF, a single PHYTOCHROME INTERACTING FACTOR gene in M. polymorpha, completely abolished the FR-HIR-dependent gametangiophore formation, while overexpression of MpPIF accelerated the response. FR-HIR-dependent transcriptional regulation was also disrupted in the Mppif mutant. Our findings suggest that plants had already acquired the FR-HIR signaling mediated by phytochrome and PIF at a very early stage during the course of land plant evolution, and that a single phytochrome in the common ancestor of land plants could mediate both LFR and FR-HIR.

SODIUM POTASSIUM ROOT DEFECTIVE1 regulates FLOWERING LOCUS T expression via the microRNA156-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE3 module in response to potassium conditions.

To determine flowering time, plants perceive multiple environmental stimuli and integrate these signals in the regulation of a florigen gene, FLOWERING LOCUS T (FT). It has been known that nutrient availability affects flowering time in both laboratories and fields. Nitrogen (N), phosphorus (P) and potassium (K) are the three major macronutrients which are important for plant growth and development. Although N and P stimuli can alter the expression of regulators of FT including microRNA156 (miR156) and miR156-targeted transcription factors of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) family, how K+ conditions affect flowering is still unclear. We focused on SODIUM POTASSUIM ROOT DEFECTIVE1 (NaKR1) whose mutant plants showed Na+ and K+ overaccumulation and late flowering. It was reported that NaKR1 is involved in the phloem transport of FT protein. Here we report that NaKR1 is also required for the promotion of FT expression in long-day conditions. NaKR1 affects the accumulation of miR156 and SPL3 expression, suggesting that NaKR1 regulates FT expression in part through the miR156-SPL3 module. The late-flowering phenotype of the nakr1-1 mutant was partially suppressed under low K+ conditions, and miR156 abundance and SPL3 expression in the nakr1-1 mutant and, to a lesser extent, in wild-type plants responded to K+ conditions. Taken together, our findings suggest that the miR156-SPL3 module mediates regulation of FT expression by NaKR1 in response to K+ conditions. Finally, we propose a model in which NaKR1 plays dual roles in regulation of flowering, one in the regulation of florigen production, the other in that of florigen transport.

Re-Evaluation of Florigen Transport Kinetics with Separation of Functions by Mutations That Uncouple Flowering Initiation and Long-Distance Transport.

In many plants, timing of flowering is regulated by day length. In Arabidopsis, florigen, FLOWERING LOCUS T (FT) protein, is synthesized in leaf phloem companion cells in response to long days and is transported to the shoot apical meristem (SAM) through the phloem. The temporal aspects of florigen transportation have been studied in various plants by physiological experiments. Nevertheless, little is known about how FT protein transportation is regulated in Arabidopsis. In this study, we performed heat shock-based transient FT induction in a single leaf blade and detected the FT protein in the shoot apex by 2D-PAGE. We demonstrated that detectable amounts of FT were transported from the leaf to the shoot apex within 8 h, and subsequent FT-induced target gene expression was detected within 8-12 h. Furthermore, we identified three amino acid residues (V70, S76 and R83) where missense mutations led to reduced mobility. Interestingly, these FT variants lost only their transportation ability, but retained their flowering promotion capacity, suggesting that discrete amino acids are involved in flowering regulation and transport regulation. Since the interaction with FT-INTERACTING PROTEIN 1 (FTIP1) was not affected in these FT variants, we hypothesize that the three amino acid residues are not involved in the FTIP1-mediated pathway of uploading, but rather in the subsequent step(s) of FT transport.

Correction to: Circadian clock during plant development.

The article" Circadian clock during plant development".