25 Years of thermomorphogenesis research: milestones and perspectives.

In 1998, Bill Gray and colleagues showed that warm temperatures trigger arabidopsis hypocotyl elongation in an auxin-dependent manner. This laid the foundation for a vibrant research discipline. With several active members of the 'thermomorphogenesis' community, we here reflect on 25 years of elevated ambient temperature research and look to the future.

HY5 and phytochrome activity modulate shoot-to-root coordination during thermomorphogenesis in Arabidopsis.

Temperature is one of the most impactful environmental factors to which plants adjust their growth and development. Although the regulation of temperature signaling has been extensively investigated for the aerial part of plants, much less is known and understood about how roots sense and modulate their growth in response to fluctuating temperatures. Here, we found that shoot and root growth responses to high ambient temperature are coordinated during early seedling development in Arabidopsis A shoot signaling module that includes HY5, the phytochromes and the PIFs exerts a central function in coupling these growth responses and maintaining auxin levels in the root. In addition to the HY5/PIF-dependent shoot module, a regulatory axis composed of auxin biosynthesis and auxin perception factors controls root responses to high ambient temperature. Taken together, our findings show that shoot and root developmental responses to temperature are tightly coupled during thermomorphogenesis and suggest that roots integrate energy signals with local hormonal inputs.

The BAP Module: A Multisignal Integrator Orchestrating Growth.

Coordination of cell proliferation, cell expansion, and differentiation underpins plant growth. To maximise reproductive success, growth needs to be fine-tuned in response to endogenous and environmental cues. This developmental plasticity relies on a cellular machinery that integrates diverse signals and coordinates the downstream responses. In arabidopsis, the BAP regulatory module, which includes the BRASSINAZOLE RESISTANT 1 (BZR1), AUXIN RESPONSE FACTOR 6 (ARF6), and PHYTOCHROME INTERACTING FACTOR 4 (PIF4) transcription factors (TFs), has been shown to coordinate growth in response to multiple growth-regulating signals. In this Opinion article, we provide an integrative view on the BAP module control of cell expansion and discuss whether its function is conserved or diversified, thus providing new insights into the molecular control of growth.

DET1 and COP1 Modulate the Coordination of Growth and Immunity in Response to Key Seasonal Signals in Arabidopsis.

Plant growth and development and outcomes of plant-microbe interactions are defined by coordinated responses to seasonal signals. The mechanisms that control the coordinated regulation of growth and immunity are not well understood. Here, we show that a common signaling module integrates environmental signals, such as photoperiod and temperature, to regulate the growth-defense balance. Key light-signaling components De-Etiolated 1 (DET1) and Constitutive Photomorphogenic 1 (COP1) negatively regulate immunity and are essential for immune modulation by photoperiod and temperature. Our results show that this is regulated by the transcription factor Phytochrome Interacting Factor 4 (PIF4), suggesting that the DET1/COP1-PIF4 module acts as a central hub for the control of growth and immunity in response to seasonal signals. These findings provide a regulatory framework for environmental signal integration.

Temperature Modulates Tissue-Specification Program to Control Fruit Dehiscence in Brassicaceae.

Plants respond to diurnal and seasonal changes in temperature by reprogramming vital developmental pathways. Understanding the molecular mechanisms that define environmental modulation of plant growth and reproduction is critical in the context of climate change that threatens crop yield worldwide. Here, we report that elevated temperature accelerates fruit dehiscence in members of the Brassicaceae family including the model plant Arabidopsis thaliana and important crop species. Arabidopsis fruit development is controlled by a network of interacting regulatory genes. Among them, the INDEHISCENT (IND) gene is a key regulator of the valve-margin tissue that mediates fruit opening, hence facilitating fruit dehiscence. We demonstrated that the valve-margin development is accelerated at higher temperature and that IND is targeted for thermosensory control. Our results reveal that IND upregulation is facilitated via temperature-induced chromatin dynamics leading to accelerated valve-margin specification and dispersal of the seed. Specifically, we show that temperature-induced changes in IND expression are associated with thermosensory H2A.Z nucleosome dynamics. These findings establish a molecular framework connecting tissue identity with thermal sensing and set out directions for the production of temperature-resilient crops.

DET1 and HY5 Control PIF4-Mediated Thermosensory Elongation Growth through Distinct Mechanisms.

Plant growth and development are defined by environmental cues. The transcription factor PHYTOCHROME INTERACTING FACTOR 4 (PIF4) is the central signaling hub that integrates environmental cues, including light and temperature, to regulate growth and development. The thermosensory mechanisms controlling the PIF4-mediated temperature response, and its integration with other environmental responses, remain poorly understood. DE-ETIOLATED 1 (DET1) and CONSTITUTIVE PHOTOMORPHOGENESIS 1 (COP1), key regulators of light signaling, have been proposed to control thermosensory growth by transcriptional regulation of PIF4, through ELONGATED HYPOCOTYL 5 (HY5). Here, we show that DET1/COP1 and HY5 regulate thermosensory elongation through distinct mechanisms. DET1 and COP1 are essential for promoting PIF4 expression and stabilizing PIF4 protein. Furthermore, HY5 inhibits elongation growth through competitive chromatin binding to PIF4 targets, not through transcriptional regulation of PIF4. Our findings reveal a mechanistic framework in which DET1/COP1 and HY5 regulatory modules act independently to regulate growth through the environmental signal integrator PIF4.

PIF4 Coordinates Thermosensory Growth and Immunity in Arabidopsis.

Temperature is a key seasonal signal that shapes plant growth. Elevated ambient temperature accelerates growth and developmental transitions [1] while compromising plant defenses, leading to increased susceptibility [2, 3]. Suppression of immunity at elevated temperature is at the interface of trade-off between growth and defense [2, 4]. Climate change and the increase in average growth-season temperatures threaten biodiversity and food security [5, 6]. Despite its significance, the molecular mechanisms that link thermosensory growth and defense responses are not known. Here we show that PHYTOCHROME INTERACTING FACTOR 4 (PIF4)-mediated thermosensory growth and architecture adaptations are directly linked to suppression of immunity at elevated temperature. PIF4 positively regulates growth and development and negatively regulates immunity. We also show that natural variation of PIF4-mediated temperature response underlies variation in the balance between growth and defense among Arabidopsis natural strains. Importantly, we find that modulation of PIF4 function alters temperature sensitivity of defense. Perturbation of PIF4-mediated growth has resulted in temperature-resilient disease resistance. This study reveals a molecular link between thermosensory growth and immunity in plants. Elucidation of the molecular mechanisms that define environmental signal integration is key to the development of novel strategies for breeding temperature-resilient disease resistance in crops.

Studying Transcription Factor Binding to Specific Genomic Loci by Chromatin Immunoprecipitation (ChIP).

Plant hormone signaling involves complex transcriptional networks, where transcription factors orchestrate the control of specific gene expression. These networks include cross talk between hormone signaling pathways, and the integration of environmental signals and the developmental program. Understanding how particular transcription factors respond and integrate specific signals is crucial in order to understand the basic mechanisms of hormonal signaling and cross talk. Studying transcription factor binding at specific genomic loci by chromatin immunoprecipitation (ChIP) is therefore a valuable technique in order to analyze transcriptional regulation. The method is based on cross-linking proteins to DNA, the isolation of chromatin, and immunoprecipitation of a transcription factor of interest. The attached DNA is then recovered and analyzed by quantitative real-time PCR in order to establish binding sites of the respective transcription factor. Here, we present a relatively simple and short protocol for ChIP on single loci.

Association of Serum Vitamin D Levels with Bacterial Load in Pulmonary Tuberculosis Patients.

BACKGROUND: Vitamin D is known to have diverse effects on various systems in the body. There is evidence to suggest that a link exists between the serum vitamin D status and tuberculosis. The present study was designed to assess the alterations in serum 25-hydroxyvitamin D levels in newly diagnosed sputum acid fast bacilli (AFB) positive pulmonary tuberculosis patients and to study the association, if any, between serum vitamin D levels and different levels of sputum smear positivity. METHODS: Serum 25-hydroxyvitamin D levels were estimated in 65 sputum AFB positive pulmonary tuberculosis patients and 65 age and gender-matched healthy controls. RESULTS: The levels of serum 25 hydroxy-vitamin D in tuberculosis patients were not statistically different from the levels of serum 25 hydroxy-vitamin D in healthy controls. However, among patients with pulmonary tuberculosis, there was a significant negative correlation between the levels of serum 25 hydroxy-vitamin D and levels of sputum positivity. CONCLUSION: Serum vitamin D levels negatively correlates with bacterial load in patients with active pulmonary tuberculosis.

SWR1 Chromatin-Remodeling Complex Subunits and H2A.Z Have Non-overlapping Functions in Immunity and Gene Regulation in Arabidopsis.

Incorporation of the histone variant H2A.Z into nucleosomes by the SWR1 chromatin remodeling complex is a critical step in eukaryotic gene regulation. In Arabidopsis, SWR1c and H2A.Z have been shown to control gene expression underlying development and environmental responses. Although they have been implicated in defense, the specific roles of the complex subunits and H2A.Z in immunity are not well understood. In this study, we analyzed the roles of the SWR1c subunits, PHOTOPERIOD-INDEPENDENT EARLY FLOWERING1 (PIE1), ACTIN-RELATED PROTEIN6 (ARP6), and SWR1 COMPLEX 6 (SWC6), as well as H2A.Z, in defense and gene regulation. We found that SWR1c components play different roles in resistance to different pathogens. Loss of PIE1 and SWC6 function as well as depletion of H2A.Z led to reduced basal resistance, while loss of ARP6 fucntion resulted in enhanced resistance. We found that mutations in PIE1 and SWC6 resulted in impaired effector-triggered immunity. Mutation in SWR1c components and H2A.Z also resulted in compromised jasmonic acid/ethylene-mediated immunity. Genome-wide expression analyses similarly reveal distinct roles for H2A.Z and SWR1c components in gene regulation, and suggest a potential role for PIE1 in the regulation of the cross talk between defense signaling pathways. Our data show that although they are part of the same complex, Arabidopsis SWR1c components could have non-redundant functions in plant immunity and gene regulation.

Delineation of metabolic gene clusters in plant genomes by chromatin signatures.

Plants are a tremendous source of diverse chemicals, including many natural product-derived drugs. It has recently become apparent that the genes for the biosynthesis of numerous different types of plant natural products are organized as metabolic gene clusters, thereby unveiling a highly unusual form of plant genome architecture and offering novel avenues for discovery and exploitation of plant specialized metabolism. Here we show that these clustered pathways are characterized by distinct chromatin signatures of histone 3 lysine trimethylation (H3K27me3) and histone 2 variant H2A.Z, associated with cluster repression and activation, respectively, and represent discrete windows of co-regulation in the genome. We further demonstrate that knowledge of these chromatin signatures along with chromatin mutants can be used to mine genomes for cluster discovery. The roles of H3K27me3 and H2A.Z in repression and activation of single genes in plants are well known. However, our discovery of highly localized operon-like co-regulated regions of chromatin modification is unprecedented in plants. Our findings raise intriguing parallels with groups of physically linked multi-gene complexes in animals and with clustered pathways for specialized metabolism in filamentous fungi.

Base mediated 7-exo-dig intramolecular cyclization of Ugi-propargyl precursors: a highly efficient and regioselective synthetic approach toward diverse 1,4-benzoxazepine-5(2H)-ones.

A metal-free facile and efficient two-step synthetic protocol for the preparation of 1,4-benzoxazepine-5(2H)-one derivatives has been developed. The protocol involves Ugi reaction followed by K2CO3 mediated highly regioselective 7-exo-dig intramolecular cyclization of less-nucleophilic oxygen with the pendant alkyne moiety of an Ugi-propargyl precursor to afford the 1,4-benzoxazepine-5(2H)-one derivatives in good to excellent yields.

Transcription factor PIF4 controls the thermosensory activation of flowering.

Plant growth and development are strongly affected by small differences in temperature. Current climate change has already altered global plant phenology and distribution, and projected increases in temperature pose a significant challenge to agriculture. Despite the important role of temperature on plant development, the underlying pathways are unknown. It has previously been shown that thermal acceleration of flowering is dependent on the florigen, FLOWERING LOCUS T (FT). How this occurs is, however, not understood, because the major pathway known to upregulate FT, the photoperiod pathway, is not required for thermal acceleration of flowering. Here we demonstrate a direct mechanism by which increasing temperature causes the bHLH transcription factor PHYTOCHROME INTERACTING FACTOR4 (PIF4) to activate FT. Our findings provide a new understanding of how plants control their timing of reproduction in response to temperature. Flowering time is an important trait in crops as well as affecting the life cycles of pollinator species. A molecular understanding of how temperature affects flowering will be important for mitigating the effects of climate change.

Phytochrome-interacting factor 4 (PIF4) regulates auxin biosynthesis at high temperature.

At high ambient temperature, plants display dramatic stem elongation in an adaptive response to heat. This response is mediated by elevated levels of the phytohormone auxin and requires auxin biosynthesis, signaling, and transport pathways. The mechanisms by which higher temperature results in greater auxin accumulation are unknown, however. A basic helix-loop-helix transcription factor, PHYTOCHROME-INTERACTING FACTOR 4 (PIF4), is also required for hypocotyl elongation in response to high temperature. PIF4 also acts redundantly with its homolog, PIF5, to regulate diurnal growth rhythms and elongation responses to the threat of vegetative shade. PIF4 activity is reportedly limited in part by binding to both the basic helix-loop-helix protein LONG HYPOCOTYL IN FAR RED 1 and the DELLA family of growth-repressing proteins. Despite the importance of PIF4 in integrating multiple environmental signals, the mechanisms by which PIF4 controls growth are unknown. Here we demonstrate that PIF4 regulates levels of auxin and the expression of key auxin biosynthesis genes at high temperature. We also identify a family of SMALL AUXIN UP RNA (SAUR) genes that are expressed at high temperature in a PIF4-dependent manner and promote elongation growth. Taken together, our results demonstrate direct molecular links among PIF4, auxin, and elongation growth at high temperature.

H2A.Z-containing nucleosomes mediate the thermosensory response in Arabidopsis.

Plants are highly sensitive to temperature and can perceive a difference of as little as 1 degrees C. How temperature is sensed and integrated in development is unknown. In a forward genetic screen in Arabidopsis, we have found that nucleosomes containing the alternative histone H2A.Z are essential to perceiving ambient temperature correctly. Genotypes deficient in incorporating H2A.Z into nucleosomes phenocopy warm grown plants, and show a striking constitutive warm temperature transcriptome. We show that nucleosomes containing H2A.Z display distinct responses to temperature in vivo, independently of transcription. Using purified nucleosomes, we are able to show that H2A.Z confers distinct DNA-unwrapping properties on nucleosomes, indicating a direct mechanism for the perception of temperature through DNA-nucleosome fluctuations. Our results show that H2A.Z-containing nucleosomes provide thermosensory information that is used to coordinate the ambient temperature transcriptome. We observe the same effect in budding yeast, indicating that this is an evolutionarily conserved mechanism.

Distress overlaps with anxiety and depression in patients with head and neck cancer.

Psychological problems in cancer patients often go unrecognized until they are specifically sought. This is more in patients with depression as they are reluctant to complain about their symptoms. The present study was carried out to evaluate the relation of distress with anxiety and depression in 123 patients with head and neck cancers using Distress Inventory for Cancer version 2 (DIC2) and the Hospital Anxiety and Depression scale (HADS). The mean DIC 2 scores were 24.6 while that of subscales ranged from 2.6 to 11.0. Fifteen patients were found to have clinical caseness for anxiety while 12 (10%) were caseness for depression. Total distress, emotional and social distress subscales were found to have positive correlation with anxiety and depression suggesting a possible overlap of two constructs. In multivariate analysis only belief in god was found to significantly affect the distress. Results of present study suggest significant psychological morbidity in head neck cancer patients undergoing curative treatment. This is the first study reporting on the psychometric properties of distress inventory on cancer version 2 since its validation, the results suggest a possible overlap of two constructs similar to that seen with other tools on distress and this may have major implications for clinical practice.

Green Alga (Chlamydomonas reinhardtii).

This protocol describes the Agrobacterium tumefaciens-mediated nuclear transformation of a microalgae Chlamydomonas reinhardtii, using a gene construct carrying the genes coding for beta-glucuronidase (gus), green fluorescent protein (gfp), and hygromycin phosphotransferase (hpt). The transformation frequency with this protocol as revealed by hygromycin resistance was many fold higher (about 50-fold) than that of the commonly used glass bead method of transformation. The simplicity of Agrobacterium-mediated gene transfer and the high transformation frequency as well as the precision of T-DNA integration will enable further molecular dissection of this important model organism as well as other algal systems to understand basic plant metabolic processes as well as to exploit the systems for biotechnological applications.