Molecular and genetic control of plant thermomorphogenesis

Temperature is a major factor governing the distribution and seasonal behaviour of plants. Being sessile, plants are highly responsive to small differences in temperature and adjust their growth and development accordingly. The suite of morphological and architectural changes induced by high ambient temperatures, below the heat-stress range, is collectively called thermomorphogenesis. Understanding the molecular genetic circuitries underlying thermomorphogenesis is particularly relevant in the context of climate change, as this knowledge will be key to rational breeding for thermo-tolerant crop varieties. Until recently, the fundamental mechanisms of temperature perception and signalling remained unknown. Our understanding of temperature signalling is now progressing, mainly by exploiting the model plant Arabidopsis thaliana. The transcription factor PHYTOCHROME INTERACTING FACTOR 4 (PIF4) has emerged as a critical player in regulating phytohormone levels and their activity. To control thermomorphogenesis, multiple regulatory circuits are in place to modulate PIF4 levels, activity and downstream mechanisms. Thermomorphogenesis is integrally governed by various light signalling pathways, the circadian clock, epigenetic mechanisms and chromatin-level regulation. In this Review, we summarize recent progress in the field and discuss how the emerging knowledge in Arabidopsis may be transferred to relevant crop systems

Calpains Mediate Integrin Attachment Complex Maintenance of Adult Muscle in Caenorhabditis elegans

Two components of integrin containing attachment complexes, UNC-97/PINCH and UNC-112/MIG-2/Kindlin-2, were recently identified as negative regulators of muscle protein degradation and as having decreased mRNA levels in response to spaceflight. Integrin complexes transmit force between the inside and outside of muscle cells and signal changes in muscle size in response to force and, perhaps, disuse. We therefore investigated the effects of acute decreases in expression of the genes encoding these multi-protein complexes. We find that in fully developed adult Caenorhabditis elegans muscle, RNAi against genes encoding core, and peripheral, members of these complexes induces protein degradation, myofibrillar and mitochondrial dystrophies, and a movement defect. Genetic disruption of Z-line– or M-line–specific complex members is sufficient to induce these defects. We confirmed that defects occur in temperature-sensitive mutants for two of the genes: unc-52, which encodes the extra-cellular ligand Perlecan, and unc-112, which encodes the intracellular component Kindlin-2. These results demonstrate that integrin containing attachment complexes, as a whole, are required for proper maintenance of adult muscle. These defects, and collapse of arrayed attachment complexes into ball like structures, are blocked when DIM-1 levels are reduced. Degradation is also blocked by RNAi or drugs targeting calpains, implying that disruption of integrin containing complexes results in calpain activation. In wild-type animals, either during development or in adults, RNAi against calpain genes results in integrin muscle attachment disruptions and consequent sub-cellular defects. These results demonstrate that calpains are required for proper assembly and maintenance of integrin attachment complexes. Taken together our data provide in vivo evidence that a calpain-based molecular repair mechanism exists for dealing with attachment complex disruption in adult muscle. Since C. elegans lacks satellite cells, this mechanism is intrinsic to the muscles and raises the question if such a mechanism also exists in higher metazoans

The Arabidopsis protein phosphatase PP2C38 negatively regulates the central immune kinase BIK1

Plants recognize pathogen-associated molecular patterns (PAMPs) via cell surface-localized pattern recognition receptors (PRRs), leading to PRR-triggered immunity (PTI). The Arabidopsis cytoplasmic kinase BIK1 is a downstream substrate of several PRR complexes. How plant PTI is negatively regulated is not fully understood. Here, we identify the protein phosphatase PP2C38 as a negative regulator of BIK1 activity and BIK1-mediated immunity. PP2C38 dynamically associates with BIK1, as well as with the PRRs FLS2 and EFR, but not with the co-receptor BAK1. PP2C38 regulates PAMP-induced BIK1 phosphorylation and impairs the phosphorylation of the NADPH oxidase RBOHD by BIK1, leading to reduced oxidative burst and stomatal immunity. Upon PAMP perception, PP2C38 is phosphorylated on serine 77 and dissociates from the FLS2/EFR-BIK1 complexes, enabling full BIK1 activation. Together with our recent work on the control of BIK1 turnover, this study reveals another important regulatory mechanism of this central immune component

Patient Complications after Interscalene Block: A Retrospective Comparison of Liposomal Bupivacaine to Nonliposomal Bupivacaine

Background. The purpose of this study was to investigate if the addition of liposome bupivacaine (LB) to an interscalene block (ISB) had an effect on the number of patients with surgical- or block-related complications. Methods. This was a single-center retrospective chart view performed by identifying patients who received an ISB from January 1, 2014, through April 26, 2018, at the University of Minnesota. 1,518 patients were identified who received an ISB (LB = 784, nonliposomal bupivacaine = 734). Patients were divided into two groups those who did receive liposome bupivacaine in their ISB and those who did not receive liposome bupivacaine in their ISB. Medical records were individually reviewed for surgical procedure, block medications, complications related to the block or surgical procedure, phone calls to the healthcare system for issues related to opioids or pain within 3 and within 30 days, readmissions within 30 days, and emergency room visits for complications within 3 and 30 days. Results. There was no significant difference in the number of patients with surgical or anesthetic complications. Only phone calls for pain within 3 days were significantly different. The LB group had 3.2% of patients call compared to 5.6% in the nonliposomal bupivacaine group (aOR = 1.71 (95% CI: 1.04–2.87), p=0.036). We found no significant difference in any of the other secondary outcomes. Conclusions. The use of LB in an ISB demonstrated no significant difference compared to nonliposomal bupivacaine in numbers of complications, emergency room visits, and readmissions

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

The SAUR19 subfamily of SMALL AUXIN UP RNA genes promote cell expansion

The plant hormone auxin controls numerous aspects of plant growth and development by regulating the expression of hundreds of genes. SMALL AUXIN UP RNA (SAUR) genes comprise the largest family of auxin-responsive genes, but their function is unknown. Although prior studies have correlated the expression of some SAUR genes with auxin-mediated cell expansion, genetic evidence implicating SAURs in cell expansion has not been reported. The Arabidopsis SAUR19, SAUR20, SAUR21, SAUR22, SAUR23, and SAUR24 (SAUR1924) genes encode a subgroup of closely related SAUR proteins. We demonstrate that these SAUR proteins are highly unstable in Arabidopsis. However, the addition of an N-terminal GFP or epitope tag dramatically increases the stability of SAUR proteins. Expression of these stabilized SAUR fusion proteins in Arabidopsis confers numerous auxin-related phenotypes indicative of increased and/or unregulated cell expansion, including increased hypocotyl and leaf size, defective apical hook maintenance, and altered tropic responses. Furthermore, seedlings expressing an artificial microRNA targeting multiple members of the SAUR1924 subfamily exhibit short hypocotyls and reduced leaf size. Together, these findings demonstrate that SAUR1924 function as positive effectors of cell expansion. This regulation may be achieved through the modulation of auxin transport, as SAUR gain-of-function and loss-of-function seedlings exhibit increased and reduced basipetal indole-3-acetic acid transport, respectively. Consistent with this possibility, SAUR1924 proteins predominantly localize to the plasma membrane