Environmental pH signals the release of monosaccharides from cell wall in coral symbiotic alga.

Reef-building corals thrive in oligotrophic environments due to their possession of endosymbiotic algae. Confined to the low pH interior of the symbiosome within the cell, the algal symbiont provides the coral host with photosynthetically fixed carbon. However, it remains unknown how carbon is released from the algal symbiont for uptake by the host.

Regulatory Modules Involved in the Degradation and Modification of Host Cell Walls During Invasion.

Haustoria of parasitic plants have evolved sophisticated traits to successfully infect host plants. The degradation and modification of host cell walls enable the haustorium to effectively invade host tissues. This study focused on two () genes and a set of the cell wall enzyme genes principally expressed during the haustorial invasion of Yuncker.

Host-produced ethylene is required for marked cell expansion and endoreduplication in dodder search hyphae.

The genus Cuscuta comprises stem holoparasitic plant species with wide geographic distribution. Cuscuta spp. obtain water, nutrients, proteins, and mRNA from their host plants via a parasitic organ called the haustorium.

Cell wall modification by the xyloglucan endotransglucosylase/hydrolase XTH19 influences freezing tolerance after cold and sub-zero acclimation.

Freezing triggers extracellular ice formation leading to cell dehydration and deformation during a freeze-thaw cycle. Many plant species increase their freezing tolerance during exposure to low, non-freezing temperatures, a process termed cold acclimation. In addition, exposure to mild freezing temperatures after cold acclimation evokes a further increase in freezing tolerance (sub-zero acclimation).

Diversity of Pectin Rhamnogalacturonan I Rhamnosyltransferases in Glycosyltransferase Family 106.

Rhamnogalacturonan I (RG-I) comprises approximately one quarter of the pectin molecules in land plants, and the backbone of RG-I consists of a repeating sequence of [2)-α-L-Rha(1-4)-α-D-GalUA(1-] disaccharide. Four genes encoding RG-I rhamnosyltransferases (AtRRT1 to AtRRT4), which synthesize the disaccharide repeats, have been identified in the glycosyltransferase family (GT106). However, the functional role of RG-I in plant cell walls and the evolutional history of RRTs remains to be clarified.

Xyloglucan Is Not Essential for the Formation and Integrity of the Cellulose Network in the Primary Cell Wall Regenerated from Protoplasts.

The notion that xyloglucans (XG) play a pivotal role in tethering cellulose microfibrils in the primary cell wall of plants can be traced back to the first molecular model of the cell wall proposed in 1973, which was reinforced in the 1990s by the identification of Xyloglucan Endotransglucosylase/Hydrolase (XTH) enzymes that cleave and reconnect xyloglucan crosslinks in the cell wall. However, this tethered network model has been seriously challenged since 2008 by the identification of the xyloglucan-deficient mutant (), which exhibits functional cell walls. Thus, the molecular mechanism underlying the physical integration of cellulose microfibrils into the cell wall remains controversial.

Root-knot nematodes modulate cell walls during root-knot formation in Arabidopsis roots.

Phytoparasitic nematodes parasitize many species of rooting plants to take up nutrients, thus causing severe growth defects in the host plants. During infection, root-knot nematodes induce the formation of a characteristic hyperplastic structure called a root-knot or gall on the roots of host plants. Although many previous studies addressed this abnormal morphogenesis, the underlying mechanisms remain uncharacterized.

Interspecific Signaling Between the Parasitic Plant and the Host Plants Regulate Xylem Vessel Cell Differentiation in Haustoria of .

The genus is stem parasitic angiosperms that parasitize a wide range of vascular plants via de novo formation of a distinctive parasitic organ called a haustorium. In the developing haustorium, meristematic cells, which are initiated from the stem cortical tissue, differentiate into haustorial parenchyma cells, which elongate, penetrate into the host tissues, and finally connect with the host vasculature. This interspecific vasculature connection allows the parasite to uptake water and nutrients from the host plant.

Pectin RG-I rhamnosyltransferases represent a novel plant-specific glycosyltransferase family.

Pectin is one of the three key cell wall polysaccharides in land plants and consists of three major structural domains: homogalacturonan, rhamnogalacturonan I (RG-I) and RG-II. Although the glycosyltransferase required for the synthesis of the homogalacturonan and RG-II backbone was identified a decade ago, those for the synthesis of the RG-I backbone, which consists of the repeating disaccharide unit [→2)-α-L-Rha-(1 → 4)-α-D-GalUA-(1→], have remained unknown. Here, we report the identification and characterization of Arabidopsis RG-I:rhamnosyltransferases (RRTs), which transfer the rhamnose residue from UDP-β-L-rhamnose to RG-I oligosaccharides.

Ethylene-gibberellin signaling underlies adaptation of rice to periodic flooding.

Most plants do poorly when flooded. Certain rice varieties, known as deepwater rice, survive periodic flooding and consequent oxygen deficiency by activating internode growth of stems to keep above the water. Here, we identify the gibberellin biosynthesis gene, (), whose loss-of-function allele catapulted the rice Green Revolution, as being responsible for submergence-induced internode elongation.

Rice leaf hydrophobicity and gas films are conferred by a wax synthesis gene (LGF1) and contribute to flood tolerance.

Floods impede gas (O and CO ) exchange between plants and the environment. A mechanism to enhance plant gas exchange under water comprises gas films on hydrophobic leaves, but the genetic regulation of this mechanism is unknown. We used a rice mutant (dripping wet leaf 7, drp7) which does not retain gas films on leaves, and its wild-type (Kinmaze), in gene discovery for this trait.

Time-Course Transcriptomics Analysis Reveals Key Responses of Submerged Deepwater Rice to Flooding.

Water submergence is an environmental factor that limits plant growth and survival. Deepwater rice () adapts to submergence by rapidly elongating its internodes and thereby maintaining its leaves above the water surface. We performed a comparative RNA sequencing transcriptome analysis of the shoot base region, including basal nodes, internodes, and shoot apices of seedlings at two developmental stages from two varieties with contrasting deepwater growth responses.

Quantitative confocal imaging method for analyzing cellulose dynamics during cell wall regeneration in Arabidopsis mesophyll protoplasts.

The network structure of cellulose fibrils provides mechanical properties to the primary cell wall, thereby determining the shapes and growth patterns of plant cells. Despite intensive studies, the construction process of the network structure remains largely unknown, mainly due to the lack of a robust, straightforward technique to evaluate network configuration. Here, we developed a quantitative confocal imaging method for general use in the study of cell wall dynamics in protoplasts derived from Arabidopsis leaf mesophyll cells.

eQTLs Regulating Transcript Variations Associated with Rapid Internode Elongation in Deepwater Rice.

To avoid low oxygen, oxygen deficiency or oxygen deprivation, deepwater rice cultivated in flood planes can develop elongated internodes in response to submergence. Knowledge of the gene regulatory networks underlying rapid internode elongation is important for an understanding of the evolution and adaptation of major crops in response to flooding. To elucidate the genetic and molecular basis controlling their deepwater response we used microarrays and performed expression quantitative trait loci (eQTL) and phenotypic QTL (phQTL) analyses of internode samples of 85 recombinant inbred line (RIL) populations of non-deepwater (Taichung 65)- and deepwater rice (Bhadua).

Arabidopsis Regenerating Protoplast: A Powerful Model System for Combining the Proteomics of Cell Wall Proteins and the Visualization of Cell Wall Dynamics.

The development of a range of sub-proteomic approaches to the plant cell wall has identified many of the cell wall proteins. However, it remains difficult to elucidate the precise biological role of each protein and the cell wall dynamics driven by their actions. The plant protoplast provides an excellent means not only for characterizing cell wall proteins, but also for visualizing the dynamics of cell wall regeneration, during which cell wall proteins are secreted.

Rare allele of a previously unidentified histone H4 acetyltransferase enhances grain weight, yield, and plant biomass in rice.

Grain weight is an important crop yield component; however, its underlying regulatory mechanisms are largely unknown. Here, we identify a grain-weight quantitative trait locus (QTL) encoding a new-type GNAT-like protein that harbors intrinsic histone acetyltransferase activity (OsglHAT1). Our genetic and molecular evidences pinpointed the QTL-OsglHAT1's allelic variations to a 1.

QTL analysis of internode elongation in response to gibberellin in deepwater rice.

Gibberellin (GA) is a plant hormone that has important roles in numerous plant developmental phases. Rice plants known as deepwater rice respond to flooding by elongating their internodes to avoid anoxia. Previous studies reported that GA is essential for internode elongation in deepwater rice.

A WUSCHEL-related homeobox 3B gene, depilous (dep), confers glabrousness of rice leaves and glumes.

Background: Glabrousness is an important agricultural trait for the practical breeding of rice. In this study, depilous (dep), the gene responsible for glabrous leaves and glumes of rice was identified by map-based cloning.

Results: The dep gene encodes a WUSCHEL-related homeobox 3B that was fine-mapped to a 22-kb region on the short arm of chromosome 5 using progenies derived from crosses between Koshihikari (pubescent) and GLSL15, an Oryza glaberrima chromosome segment substitution line (glabrous).

Two novel QTLs regulate internode elongation in deepwater rice during the early vegetative stage.

Deepwater rice possesses internode elongation ability to avoid drowning under deepwater conditions. Previous studies identified three QTLs regulating internode elongation ability on chromosomes 1, 3 and 12 using different populations. However, these QTLs only induce internode elongation in response to deepwater conditions from the 7-leaf stage and not during the early leaf stage.

Direct interaction of ligand-receptor pairs specifying stomatal patterning.

Valves on the plant epidermis called stomata develop according to positional cues, which likely involve putative ligands (EPIDERMAL PATTERNING FACTORS [EPFs]) and putative receptors (ERECTA family receptor kinases and TOO MANY MOUTHS [TMM]) in Arabidopsis. Here we report the direct, robust, and saturable binding of bioactive EPF peptides to the ERECTA family. In contrast, TMM exhibits negligible binding to EPF1 but binding to EPF2.

Arabidopsis lonely guy (LOG) multiple mutants reveal a central role of the LOG-dependent pathway in cytokinin activation.

Cytokinins are phytohormones that play key roles in the maintenance of stem cell activity in plants. Although alternative single-step and two-step activation pathways for cytokinin have been proposed, the significance of the single-step pathway which is catalyzed by LONELY GUY (LOG), is not fully understood. We analyzed the metabolic flow of cytokinin activation in Arabidopsis log multiple mutants using stable isotope-labeled tracers and characterized the mutants' morphological and developmental phenotypes.

Functional analyses of LONELY GUY cytokinin-activating enzymes reveal the importance of the direct activation pathway in Arabidopsis.

Cytokinins play crucial roles in diverse aspects of plant growth and development. Spatiotemporal distribution of bioactive cytokinins is finely regulated by metabolic enzymes. LONELY GUY (LOG) was previously identified as a cytokinin-activating enzyme that works in the direct activation pathway in rice (Oryza sativa) shoot meristems.

Identification of Arabidopsis subtilisin-like serine protease specifically expressed in root stele by gene trapping.

Xylem plays a role not only in the transport of water and nutrients but also in the regulation of growth and development through the transport of biologically active substances. In addition to mineral salts, xylem sap contains hormones, organic nutrients and proteins. However, the physiological functions of most of those substances remain unclear.