関: chromoplast、leukoplast、plastid

WordNet

any of various small particles in the cytoplasm of the cells of plants and some animals containing pigments or starch or oil or protein
plastid containing pigments other than chlorophyll usually yellow or orange carotenoids

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/04/17 14:43:53」(JST)

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Amyloplasts in a potato cell

Types of plastid

Amyloplasts are non-pigmented organelles found in some plant cells. They are responsible for the synthesis and storage of starch granules, through the polymerization of glucose.^[1] Amyloplasts also convert this starch back into sugar when the plant needs energy. Large numbers of amyloplasts can be found in fruit and in underground storage tissues of some plants, such as in potato tubers.

Amyloplasts are plastids, specifically leucoplasts. Plastids are a specialized class of cellular organelles that carry their own genome and are believed to be descendants of cyanobacteria (blue-green algae) which formed a symbiotic relationship with the eukaryotic cell.

Starch synthesis and storage also takes place in chloroplasts, a type of pigmented plastid involved in photosynthesis. Amyloplasts and chloroplasts are closely related, and amyloplasts can turn into chloroplasts; this is for instance observed when potato tubers are exposed to light and turn green.^[2]

Statoliths: sensing gravity

In the root cap (a tissue at the tip of the root) there is a special subset of cells, called statocytes. Inside the statocyte cells, some specialized amyloplasts are involved in the perception of gravity by the plant (gravitropism). These specialized amyloplasts—called statoliths—are denser than the cytoplasm and can sediment according to the gravity vector. The statoliths are enmeshed in a web of actin and it is thought that their sedimentation transmits the gravitropic signal by activating mechanosensitive channels. The gravitropic signal then leads to the reorientation of auxin efflux carriers and subsequent redistribution of auxin streams in the root cap and root as a whole. The changed relations in concentration of auxin leads to differential growth of the root tissues. Taken together, the root is then turning to follow the gravity stimuli. Statoliths are also found in the endodermic layer of the inflorescence stem. The redistribution of auxin causes the shoot to turn in a direction opposite that of the gravity stimuli.^{[citation needed]}

References

^ Wise, Robert (2007). "1". The Diversity of Plastid Form and Function. Springer.
^ Anstis, P. J. P.; D. H. Northcote (1973). "Development of chloroplasts from amyloplasts in potato tuber discs". New Phytologist 72 (3): 449–463. doi:10.1111/j.1469-8137.1973.tb04394.x.

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English Journal

The rise and fall of Picobiliphytes: How assumed autotrophs turned out to be heterotrophs.

Moreira D1, López-García P.Author information 1Unité d'Ecologie, Systématique et Evolution, CNRS UMR8079, Université Paris-Sud, Orsay, France.AbstractAlgae are significant members of Earth's biodiversity. Having been studied for a long time, the discovery of new algal phyla is extremely unusual. Recently, the enigmatic "Picobiliphyta," a group of uncultured eukaryotes unveiled using molecular tools, were claimed to represent an unrecognized early branching algal lineage with a nucleomorph (remnant nucleus of a secondary algal endosymbiont) in their plastids. However, subsequent studies rejected the presence of a nucleomorph, and single-cell genomic studies failed to detect any plastid-related genes, ruling out the possibility of plastid occurrence. The isolation of the first "picobiliphyte," Picomonas judraskeda, a tiny organism that feeds on very small (<150 nm) organic particles, came as final proof of their non-photosynthetic lifestyle. Consequently, the group has been renamed Picozoa. The passage from "picobiliphytes" to "picozoa" illustrates the crucial role that classical protistology should play to provide sound biological context for the wealth of data produced by modern molecular techniques.
BioEssays : news and reviews in molecular, cellular and developmental biology.Bioessays.2014 May;36(5):468-74. doi: 10.1002/bies.201300176. Epub 2014 Mar 10.
Algae are significant members of Earth's biodiversity. Having been studied for a long time, the discovery of new algal phyla is extremely unusual. Recently, the enigmatic "Picobiliphyta," a group of uncultured eukaryotes unveiled using molecular tools, were claimed to represent an unrecognized early
PMID 24615955

A Soybean Acyl Carrier Protein, GmACP, Is Important for Root Nodule Symbiosis.

Wang J, Tóth K, Tanaka K, Nguyen CT, Yan Z, Brechenmacher L, Dahmen J, Chen M, Thelen JJ, Qiu L, Stacey G.AbstractLegumes (members of family Fabaceae) establish a symbiotic relationship with nitrogen-fixing soil bacteria (rhizobia) to overcome nitrogen source limitation. Single root hair epidermal cells serve as the entry point for bacteria to infect the host root, leading to development of a new organ, the nodule, which the bacteria colonize. In the present study, the putative role of a soybean acyl carrier protein (ACP), GmACP (Glyma18g47950), was examined in nodulation. ACP represent an essential cofactor protein in fatty acid biosynthesis. Phylogenetic analysis of plant ACP protein sequences showed that GmACP was classified in a legume-specific clade. Quantitative reverse-transcription polymerase chain reaction analysis demonstrated that GmACP was expressed in all soybean tissues but showed higher transcript accumulation in nodule tissue. RNA interference-mediated gene silencing of GmACP resulted in a significant reduction in nodule numbers on soybean transgenic roots. Fluorescent protein-labeled GmACP was localized to plastids in planta, the site of de novo fatty acid biosynthesis in plants. Analysis of the fatty acid content of root tissue silenced for GmACP expression, as determined by gas chromatography-mass spectrometry, showed an approximately 22% reduction, specifically in palmitic and stearic acid. Taken together, our data provide evidence that GmACP plays an important role in nodulation.
Molecular plant-microbe interactions : MPMI.Mol Plant Microbe Interact.2014 May;27(5):415-23. doi: 10.1094/MPMI-09-13-0269-R.
Legumes (members of family Fabaceae) establish a symbiotic relationship with nitrogen-fixing soil bacteria (rhizobia) to overcome nitrogen source limitation. Single root hair epidermal cells serve as the entry point for bacteria to infect the host root, leading to development of a new organ, the nod
PMID 24400939

Overexpression of SrUGT85C2 from Stevia reduced growth and yield of transgenic Arabidopsis by influencing plastidial MEP pathway.

Guleria P1, Masand S1, Yadav SK2.Author information 1Biotechnology Division, CSIR-Institute of Himalayan Bioresource Technology, Palampur 176061, HP, India; Academy of Scientific and Innovative Research, New Delhi, India.2Biotechnology Division, CSIR-Institute of Himalayan Bioresource Technology, Palampur 176061, HP, India; Academy of Scientific and Innovative Research, New Delhi, India. Electronic address: sudeshkumar@ihbt.res.in.AbstractThe transcript expression of a gene SrUGT85C2 has been documented for direct relation with steviol glycoside content in Stevia plant. Steviol glycoside and gibberellin biosynthetic routes are divergent branches of methyl erythritol-4 phosphate (MEP) pathway. So, SrUGT85C2 might be an influencing gibberellin content. Hence in the present study, transgenic Arabidopsis thaliana overexpressing SrUGT85C2 cDNA from Stevia rebaudiana was developed to check its effect on gibberellin accumulation and related plant growth parameters. The developed transgenics showed a noteworthy decrease of 78-83% in GA3 content. Moreover, the transgenics showed a gibberellin deficient phenotype comprising stunted hypocotyl length, reduced shoot growth and a significant fall in relative water content. Transgenics also showed 17-37 and 64-76% reduction in chlorophyll a and chlorophyll b contents, respectively. Reduction in photosynthetic pigments could be responsible for the noticed significant decrease in plant biomass. Like steviol glycoside and gibberellin biosynthesis, chlorophyll biosynthesis also occurs from the precursors isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) of MEP pathway in the plastids. The observed downregulated expression of genes encoding MEP pathway enzymes geranyl geranyl diphosphate synthase (GGDPS), copalyl diphosphate synthase (CDPS), kaurenoic acid oxidase (KAO), chlorophyll synthetase and chlorophyll a oxygenase in transgenics overexpressing SrUGT85C2 might be responsible for the reduction in gibberellins as well as chlorophyll. This study has documented for the first time the regulatory role of SrUGT85C2 in the biosynthesis of steviol glycoside, gibberellins and chlorophyll.
Gene.Gene.2014 Apr 15;539(2):250-7. doi: 10.1016/j.gene.2014.01.071. Epub 2014 Feb 8.
The transcript expression of a gene SrUGT85C2 has been documented for direct relation with steviol glycoside content in Stevia plant. Steviol glycoside and gibberellin biosynthetic routes are divergent branches of methyl erythritol-4 phosphate (MEP) pathway. So, SrUGT85C2 might be an influencing gib
PMID 24518812