Biology subjects

Kawai-Yamada, M.

Publications and source records attributed to Kawai-Yamada, M..

4 recordsLinked to original sources

bioRxiv2024

LATE MERISTEM IDENTITY2 regulates cuticle formation on the seed surface and influences seed longevity

The seed coat protects the embryo from severe external environment. Like the aerial plant parts, the exterior surface of the seed coat is surrounded by a cuticle consisting of lipid polyesters and wax. However, the protective role of the cuticle in mature seeds has not been characterized. We herein study the transcriptional regulation of cuticle formation on the seed surface, which influences seed longevity. A chimeric repressor of Arabidopsis thaliana R2R3 MYB transcription factor gene LATE MERISTEM IDENTITY2 (LMI2) and a Torenia fournieri ortholog (TfMYBML3) was expressed in A. thaliana and T. fournieri, respectively. These lines and A. thaliana LMI2 T-DNA insertion lines were analyzed for cuticle deficiencies. A. thaliana LMI2 mutants and chimeric repressor lines exhibited a similar cuticle deficiency in immature seeds. Transmission electron microscopy observations, polyester composition analyses, and gene expression investigations revealed that LMI2 plays an essential role in cuticle development in the seed coat epidermis by regulating cutin biosynthesis. The lmi2-2 mutant exhibited shorter seed longevity than the wild-type controls in an accelerated aging test. These results indicate that LMI2 is a key regulator of cuticle formation in the seed coat, and is important for maintaining seed longevity. Significance statementCuticle is well known to have multiple important roles for surviving in the terrestrial environment, but their specific role on the seed coat and transcriptional regulation have not yet been elucidated. Here we show that LATE MERISTEM IDENTITY 2, encoding a transcription factor regulating floral meristem transition, is required for seed cuticle formation and maintaining seed longevity, providing evidence for a link between surface cuticle and seed longevity.

plant biology↗

bioRxiv2021

Intraspecific interaction of host plant influences local distribution of specialist herbivores through metabolic alterations in leaves

O_LIRecent studies suggest that changes in leaf traits due to interactions between plants affect the resource utilisation and distribution of herbivores. However, this has not yet been confirmed experimentally. Here, we investigated the effects of phenotypic plasticity in leaf traits of Rumex obtusifolius (host plant) in response to the intra- and interspecific interaction on distribution of two leaf beetles, Gastrophysa atrocyanea (specialist herbivore) and Galerucella grisescens (generalist herbivore). C_LIO_LIWe investigated the local population density of R. obtusifolius plants and the presence of leaf beetles on the plants at five study sites. Leaf chemicals (condensed tannins and total phenolics) were compared between aggregated and solitary R. obtusifolius plants. To clarify the effects of the interaction environment of R. obtusifolius plants on their leaf traits and resource utilisation by leaf beetles, we conducted cultivation and preference experiments. Leaf chemicals (chlorophylls, organic acids, primary metabolites, condensed tannins and total phenolics) and preferences of adult leaf beetles were compared between intraspecific, interspecific plant interaction, or no-interaction treatments. Finally, we evaluated the effects of interaction between R. obtusifolius on leaf beetle distribution in mesocosm experiments. C_LIO_LIIn the field, the presence of the specialist leaf beetle, G. atrocyanea, was positively correlated with the local population density (rosette overlap ratio) of R. obtusifolius plants; however, no correlation was observed in the case of the generalist leaf beetle, G. grisescens. In the cultivation experiment, plants in the intraspecific interaction treatment increased their leaf contents of condensed tannins and total phenolics, and G. atrocyanea consumed more of these leaves than leaves in other treatments. Similar results were observed in the field. In the mesocosm experiment, larger numbers of G. atrocyanea were distributed on R. obtusifolius plants exposed to below-ground intraspecific interaction than on plants not exposed to intraspecific interaction. C_LIO_LIOur results provide experimental evidence that leaf-trait changes in response to intraspecific interaction between host plants influence specialist herbivore distribution. This highlights the need to integrate plant-plant interactions into our understanding of plant-animal interactions. C_LI

ecology↗

bioRxiv2019

Excessive assimilation of ammonium by plastidic glutamine synthetase is a major cause of ammonium toxicity in Arabidopsis thaliana

Plants use nitrate and ammonium in the soil as their main nitrogen sources. Recently, ammonium has attracted attention due to evidence suggesting that, in C3 species, an elevated CO2 environment inhibits nitrate assimilation. However, high concentrations of ammonium as the sole nitrogen source for plants causes impaired growth, i.e. ammonium toxicity. Although ammonium toxicity has been studied for a long time, the primary cause remains to be elucidated. Here, we show that ammonium assimilation in plastids rather than ammonium accumulation is a primary cause for toxicity. Our genetic screen of ammonium-tolerant Arabidopsis lines with enhanced shoot growth identified plastidic GLUTAMINE SYNTHETASE 2 (GLN2) as the causal gene. Our reciprocal grafting of wild-type and GLN2 or GLN1;2-deficient lines suggested that shoot GLN2 activity results in ammonium toxicity, whilst root GLN1;2 activity prevents it. With exposure to toxic levels of ammonium, the shoot GLN2 reaction produced an abundance of protons within cells, thereby elevating shoot acidity and stimulating expression of acidic stress-responsive genes. Application of an alkaline ammonia solution to the toxic ammonium medium efficiently alleviated the ammonium toxicity with a concomitant reduction in shoot acidity. Consequently, we conclude that a primary cause of ammonium toxicity is acidic stress in the shoot. This fundamental insight provides a framework for enhanced understanding of ammonium toxicity in plants.

plant biology↗

bioRxiv2018

GONST2 transports GDP-Mannose for sphingolipid glycosylation in the Golgi apparatus of Arabidopsis

The Golgi lumen is the site of many different glycosylation events, including cell wall polysaccharide biosynthesis and lipid glycosylation. Transporters are necessary for the import of the substrates required for glycosylation (nucleotide sugars) from the cytosol where they are synthesized. Plants use four GDP-linked sugars to glycosylate macromolecules: GDP-L-Fucose, GDP-D-Mannose, GDP-L-Galactose and GDP-D-Glucose. Of the predicted fifty-one members of the nucleotide sugar transporter/triose phosphate transporter family in Arabidopsis, only four appear to contain the conserved motif needed for the transport of GDP-linked sugars, GOLGI LOCALIZED NUCLEOTIDE SUGAR TRANSPORTER (GONST) 1-4. Previously, we have demonstrated that GONST1 provides GDP-D-Mannose for glycosylation of a class of sphingolipids, the glycosylinositolphosphorylceramides (GIPCs). Here, we characterize its closest homologue, GONST2, and conclude that it also specifically provides substrate for GIPC glycosylation. Expression of GONST2 driven by the GONST1 promoter is able to rescue the severe growth phenotype of gonst1. Loss of GONST2 exacerbates the gonst1 constitutive hypersensitive response, as well as the reduced cell wall cellulose content. The gonst2 mutant grows normally under standard conditions, but has enhanced resistance to the powdery mildew-causing fungus Golovinomyces orontii.

plant biology↗