Cell Wall Remodeling Proteins Research Articles

Characterization of the PHOSPHATE RESPONSE 2-dependent and -independent Pi-starvation response secretome in rice.

Many proteins secreted from plant cells into the surrounding extracellular space help maintain cell structure and regulate stress responses in the external environment. In this study, under Pi-replete and depleted conditions, 652 high-confidence secreted proteins were quantified from wild-type (WT) and PHOSPHATE RESPONSE 2 (OsPHR2)-overexpressing suspension-cultured cells (SCCs). These proteins were functionally grouped as phosphatases, signal transduction proteins, pathogen-related (PR) proteins, cell wall-remodeling proteins, and reactive oxygen species (ROS) metabolism proteins. Although PHOSPHATE RESPONSE (PHR) transcription factors regulate two-thirds of Pi-responsive genes at the transcriptional level, only 30.6% of the Pi-starvation-regulated secreted proteins showed significant changes in OsPHR2-overexpressing SCCs. The OsPHR2-dependent systemic Pi signaling pathway mainly regulates phosphatases and PR proteins, which are involved in the utilization of organophosphate, pathogen resistance, and colonization by rhizosphere microorganisms. The OsPHR2-independent local Pi signaling pathway, on the other hand, largely regulated ROS metabolism proteins, cell wall-remodeling proteins, and signal transduction proteins, which are involved in modifying cell wall structure and root architecture. The functions of differentially expressed secreted proteins between WT and OsPHR2-overexpressing plants under Pi-sufficient and Pi-deficient conditions were further confirmed by analysis of the acid phosphatase activity, ROS content, and cell wall composition.

Physio-biochemical and proteomic mechanisms of coronatine induced potassium stress tolerance in xylem sap of cotton

Potassium (K) is a major plant nutrient, and its deficiency can limit plant growth and development. Coronatine (COR) could increase cotton seedling tolerance to K deficiency, which was hypothesized to be in relation to improving the physiological and proteomic profile of xylem sap. To test this hypothesis, cotton seedlings growth, physio-biochemical and proteomic profile of xylem sap treated with (0 and 10 nM COR) under deficient K solution (0.05 mM KCl) were explored. Compared with control, COR treatment significantly increased lateral root number and root diameter and decreased contents of malondialdehyde (MDA), some cations like potassium and calcium in xylem sap and its volume. These morphological and physiological presentations were well evidenced by differentially expressed proteins (DEPs) in the xylem sap. For instance, increasing the average root diameter and lateral roots were related to up-regulation of cobalamin-independent methionine synthase family proteins, auxin-responsive protein, and cell wall remodeling proteins such as dirigent-like protein, laccase, and the pectin lyase; lessening xylem sap volume and some cations contents was in connections with down-regulation of uclacyanin 1 and up-regulation of calmodulin-domain protein kinase 7; the MDA content reducing was associated with many PCD-related proteins’ down-regulation or loss. Furthermore, COR potentially weakened plant defense, owing to lessening or disappearing lipid-transfer proteins, signaling proteins, and other proteins positively involved in plant defense.

Building a Flower: The Influence of Cell Wall Composition on Flower Development and Reproduction.

Floral patterning is a complex task. Various organs and tissues must be formed to fulfill reproductive functions. Flower development has been studied, mainly looking for master regulators. However, downstream changes such as the cell wall composition are relevant since they allow cells to divide, differentiate, and grow. In this review, we focus on the main components of the primary cell wall—cellulose, hemicellulose, and pectins—to describe how enzymes involved in the biosynthesis, modifications, and degradation of cell wall components are related to the formation of the floral organs. Additionally, internal and external stimuli participate in the genetic regulation that modulates the activity of cell wall remodeling proteins.

Pectin Methylesterases: Cell Wall Remodeling Proteins Are Required for Plant Response to Heat Stress.

Heat stress (HS) is expected to be of increasing worldwide concern in the near future, especially with regard to crop yield and quality as a consequence of rising or varying temperatures as a result of global climate change. HS response (HSR) is a highly conserved mechanism among different organisms but shows remarkable complexity and unique features in plants. The transcriptional regulation of HSR is controlled by HS transcription factors (HSFs) which allow the activation of HS-responsive genes, among which HS proteins (HSPs) are best characterized. Cell wall remodeling constitutes an important component of plant responses to HS to maintain overall function and growth; however, little is known about the connection between cell wall remodeling and HSR. Pectin controls cell wall porosity and has been shown to exhibit structural variation during plant growth and in response to HS. Pectin methylesterases (PMEs) are present in multigene families and encode isoforms with different action patterns by removal of methyl esters to influencing the properties of cell wall. We aimed to elucidate how plant cell walls respond to certain environmental cues through cell wall-modifying proteins in connection with modifications in cell wall machinery. An overview of recent findings shed light on PMEs contribute to a change in cell-wall composition/structure. The fine-scale modulation of apoplastic calcium ions (Ca2+) content could be mediated by PMEs in response to abiotic stress for both the assembly and disassembly of the pectic network. In particular, this modulation is prevalent in guard cell walls for regulating cell wall plasticity as well as stromal aperture size, which comprise critical determinants of plant adaptation to HS. These insights provide a foundation for further research to reveal details of the cell wall machinery and stress-responsive factors to provide targets and strategies to facilitate plant adaptation.

Probing for Binding Regions of the FtsZ Protein Surface through Site-Directed Insertions: Discovery of Fully Functional FtsZ-Fluorescent Proteins.

One model for the Z-ring structure proposes that protofilaments are assembled into ribbons by lateral bonds between FtsZ subunits. Our study excluded the involvement of the front and back faces of the protofilament in essential interactions in vivo but pointed to two potential lateral bond sites, on the right and left sides. We also identified an FtsZ loop where various fluorescent proteins could be inserted without blocking function; these FtsZ-FPs functioned as the sole source of FtsZ. This advance provides improved tools for all fluorescence imaging of the Z ring and may be especially important for superresolution imaging.

Expansins: Cell Wall Remodeling Proteins with a Potential Function in Plant Defense

Cell wall (CW) performs a number of important functions. This distinctive feature of plants determines cell structure, and plays major roles in intercellular communication and plant-microbe interactions, including defense responses against potential pathogens. Expansins are novel plant CW loosening proteins, are mainly involved in the pH-dependent extension of plant CWs that is called acid growth [1,2]. These plant CW remodeling proteins have important roles in plant cell growth, fruit softening, abscission, and emergence of root hairs, pollen tube invasion of the stigma and style, meristem function, pathogenicity and developmental processes. Expansins are linked with cell growth and CW changes that are induced by a number of plant hormones. In plants, two main families of expansin genes have been discovered: -expanins (

EXPANSINA17 Up-Regulated by LBD18/ASL20 Promotes Lateral Root Formation During the Auxin Response

Expansins are non-hydrolytic cell wall-loosening proteins involved in a variety of plant developmental processes during which cell wall modification occurs. Cell wall remodeling proteins including expansins have been suggested to be involved in cell separation to facilitate the emergence of lateral roots (LRs) through the overlaying tissues of the primary root. LBD18/ASL20 activates EXPANSINA14 (EXPA14) expression by directly binding to the EXPA14 promoter to enhance LR emergence in Arabidopsis thaliana. Here we show that EXPA17 is another target gene regulated by LBD18 to promote LR formation in Arabidopsis. We showed that nuclear translocation of the LBD18:GR fusion protein expressed under the Cauliflower mosaic virus (CaMV) 35S promoter or under the LBD18 promoter by dexamethasone treatment results in an increase in EXPA17 transcript levels. β-Glucuronidase (GUS) expression under the EXPA17 promoter, which is detected only in the roots of the wild type, was reduced in the LR primordium and overlaying tissues in an lbd18 mutant background. The number of emerged LRs of the EXPA17 RNAi (RNA interference) Arabidopsis lines was significantly lower than that of the wild type. Overexpression of EXPA17 in Arabidopsis increased the density of emerged LRs in the presence of auxin compared with the wild type. LR induction experiments with a gravitropic stimulus showed that LR emergence is delayed in the EXPA17 RNAi plants compared with the wild type. In addition, EXPA4 expression was also detected in overlaying tissues of the LR primordium and was inducible by LBD18. Taken together, these results support the notion that LBD18 up-regulates a subset of EXP genes to enhance cell separation to promote LR emergence in Arabidopsis.

The RNA-Binding Protein Rrm4 is Essential for Efficient Secretion of Endochitinase Cts1

Long-distance transport of mRNAs is crucial in determining spatio-temporal gene expression in eukaryotes. The RNA-binding protein Rrm4 constitutes a key component of microtubule-dependent mRNA transport in filaments of Ustilago maydis. Although a number of potential target mRNAs could be identified, cellular processes that depend on Rrm4-mediated transport remain largely unknown. Here, we used differential proteomics to show that ribosomal, mitochondrial, and cell wall-remodeling proteins, including the bacterial-type endochitinase Cts1, are differentially regulated in rrm4Δ filaments. In vivo UV crosslinking and immunoprecipitation and fluorescence in situ hybridization revealed that cts1 mRNA represents a direct target of Rrm4. Filaments of cts1Δ mutants aggregate in liquid culture suggesting an altered cell surface. In wild type cells Cts1 localizes predominantly at the growth cone, whereas it accumulates at both poles in rrm4Δ filaments. The endochitinase is secreted and associates most likely with the cell wall of filaments. Secretion is drastically impaired in filaments lacking Rrm4 or conventional kinesin Kin1 as well as in filaments with disrupted microtubules. Thus, Rrm4-mediated mRNA transport appears to be essential for efficient export of active Cts1, uncovering a novel molecular link between mRNA transport and the mechanism of secretion.

Temporal and spatial regulation of gene expression during asexual development of Neurospora crassa.

In this study we profiled spatial and temporal transcriptional changes during asexual sporulation in the filamentous fungus Neurospora crassa. Aerial tissue was separated from the mycelium to allow detection of genes specific to each tissue. We identified 2641 genes that were differentially expressed during development, which represents ∼25% of the predicted genes in the genome of this model fungus. On the basis of the distribution of functional annotations of 1102 of these genes, we identified gene expression patterns that define key physiological events during conidial development. Not surprisingly, genes encoding transcription factors, cell wall remodeling proteins, and proteins involved in signal transduction were differentially regulated during asexual development. Among the genes differentially expressed in aerial tissues the majority were unclassified and tended to be unique to ascomycete genomes. This finding is consistent with the view that these genes evolved for asexual development in the Pezizomycotina. Strains containing deletions of several differentially expressed genes encoding transcription factors exhibited asexual development-associated phenotypes. Gene expression patterns during asexual development suggested that cAMP signaling plays a critical role in the transition from aerial growth to proconidial chain formation. This observation prompted us to characterize a deletion of the gene encoding a high-affinity cAMP phosphodiesterase (NCU00478). NCU00478 was determined to be allelic to aconidiate-2, a previously identified genetic locus controlling conidiation.

Cbk1 Regulation of the RNA-Binding Protein Ssd1 Integrates Cell Fate with Translational Control

Spatial control of gene expression, at the level of both transcription and translation, is critical for cellular differentiation [1-4]. In budding yeast, the conserved Ndr/warts kinase Cbk1 localizes to the new daughter cell, where it acts as a cell fate determinant. Cbk1 both induces a daughter-specific transcriptional program and promotes morphogenesis in a less well-defined role [5-8]. Cbk1 is essential in cells expressing functional Ssd1, an RNA-binding protein of unknown function [9-11]. We show here that Cbk1 inhibits Ssd1 in vivo. Loss of this regulation dramatically slows bud expansion, leading to highly aberrant cell wall organization at the site of cell growth. Ssd1 associates with specific mRNAs, a significant number of which encode cell wall remodeling proteins. Translation of these messages is rapidly and specifically suppressed when Cbk1 is inhibited; this suppression requires Ssd1. Transcription of several of these Ssd1-associated mRNAs is also regulated by Cbk1, indicating that the kinase controls both the transcription and translation of daughter-specific mRNAs. This work suggests a novel system by which cells coordinate localized expression of genes involved in processes critical for cell growth and division.