Документ взят из кэша поисковой машины. Адрес оригинального документа : http://kodomo.cmm.msu.ru/~ksenia_yashina/projects/Oyellows_en.doc Дата изменения: Sun Oct 19 22:08:04 2008 Дата индексирования: Tue Oct 2 15:12:42 2012 Кодировка:

Description of O.Yellows phytoplasma, OY-M, and its proteome

K. Yashina

Introduction.

Taxonomy:
> Group Tenericutes
> Class Mollicutes
> Order Acholeplasmatales
> Family Acholeplasmataceae
> Genus Candidatus Phytoplasma
> Species Onion yellows
> Strain OY-M

Structure:
Virions filamentous; not enveloped; usually flexuous; with no clear modal
length; of 772 and 823 nm (Schmidt and Schmelzer, 1978)). Axial canal
obscure. Basic helix obscure.

Habitat:
From minus 4 to 60-65 њC, life expectation: 2-3 days, infectivity of sap
not changed by treatment with di-ethyl ether, leaf sap contains few
virions. Probably distributed worldwide.

Phytoplasmas are a group of microscopic organisms that cause over 700
diseases in plants. Phytoplasmas grow and multiply within host plants and
insect vectors. In host plants, phytoplasmas are found only in the phloem
tissue of leaves, stems, and roots. When the concentration of phytoplasmas
within the plant reaches a certain level, it is believed to cause hormonal
imbalance, resulting in the development of symptoms such as chlorotic
leaves, stunting, flower petals changing to a green color (phyllody or
virescence), and witches-broom (shoot proliferation).
(Source http://www.ctahr.hawaii.edu/watercress/IP-20%5B1%5D.pdf)

***

Onion yellows phytoplasma causes a yellowing disease in onions
Phytoplasmas associated with yellows diseases were firstly described in
1926 by Kunkle in American aster plants showing virescence and flower
malformations. Since then the etiological agent of this and of similar
diseases was believed to be a virus; until in 1967 Doi et al. detected
under electron microscope phytoplasmas in aster and other plants with
"yellows" symptoms opening phytoplasmology history.
Like other mollicutes, phytoplasmas lack cell walls, are pleomorphic and
reside endocellularly in insects and plant phloem. Onion yellows
phytoplasma is a parasite that lives inside leafhopper insects and spreads
to plants through the saliva of feeding insects.
The metabolic pathways and host interactions of Onion yellows phytoplasma
is of interest in agricultural and basic sciences. The inability to culture
phytoplasmas in vitro has hindered their characterization at the molecular
level, the determination of factors involved in their pathogenicity and the
discovery of effective ways to control or cure phytoplasma diseases.
Analysis of the phytoplasma genome suggests reductive evolution as a
consequence of its life as an intracellular parasite in a nutrient-rich
environment and shows that phytoplasma lacks several genes previously
considered to be essential for autonomously replicating cells. Instead, it
possesses transporter genes involved in the uptake of substances from the
cytoplasm of surrounding host cells. Although it is difficult to define the
minimal genome concept for pathogens and symbionts that rely on their
hosts, phytoplasmas are unique bacteria that contain a new minimal gene
set.
Source:
http://www.ebi.ac.uk/2can/genomes/bacteria/Onion_yellows_phytoplasma.html

[pic]
Phytoplasma Onion yellows (left) is transmitted by Macrosteles striifrons
(right) specifically
(source http://narc.naro.affrc.go.jp/narc-e/page7/p7.html)

***

Annotation of one of the articles about O.Yellows:
Source http://mic.sgmjournals.org/cgi/reprint/150/1/135.pdf

Secretion of immunodominant membrane protein from onion yellows phytoplasma
through the Sec protein-translocation system in Escherichia coli
A gene that encodes a putative SecE protein, which is a component of the
Sec protein-translocation
system, was cloned from the onion yellows phytoplasma (OY). The
identification of this gene
and the previously reported genes encoding SecA and SecY provides evidence
that the Sec
system exists in phytoplasma. In addition, a gene encoding an antigenic
membrane protein (Amp)
(a type of immunodominant membrane protein) of OY was cloned and sequenced.
The OY
amp gene consisted of 702 nt encoding a protein of 233 aa which was highly
similar to Amp of
Aster yellows phytoplasma (AY). Part of OY Amp was overexpressed in
Escherichia coli,
purified, and used to raise an anti-Amp polyclonal antibody. The anti-Amp
antibody reacted
specifically with an OY-infected plant extract in Western blot analysis and
was therefore useful
for the detection of OY as well as Amp. Amp has a conserved protein motif
that is known to be
exported by the Sec system of E. coli. A partial OY Amp protein expressed
in E. coli was localized
in the periplasm as a shorter, putatively processed form of the protein. It
had probably been
exported from the cytoplasm to the periplasm through the Sec system.
Moreover, OY Amp protein
expressed in OY and detected in OY-infected plants was apparently also
processed. Because
phytoplasmas cannot be cultured or transformed, little information is
available regarding their
protein secretion systems. This study suggests that the Sec system operates
in this phytoplasma to
export OY Amp.


Genome and proteome of O.Yellows phytoplasma:

Genome statistics
Source
http://www.ebi.ac.uk/integr8/OrganismStatsAction.do?orgProteomeId=659

|Component |Protei|Type|Length(bp)|Av.CDS |GC |CDS |Gene |
|name |n | | |length |conten|coverage |count|
| |count | | | |t | | |
| |751 |[pic|853092 |830.341|27% |73% |751 |
|Chromosome | |] | | | | | |
| |2 |[pic|5025 |810 |24.7% |32% |2 |
|Plasmid | |] | | | | | |
|EcOYM | | | | | | | |
| |1 |[pic|1134 |1134 |23.2% |100% |1 |
|Plasmid | |] | | | | | |
|pOYM | | | | | | | |
| |
|[pic] |
|Phytoplasma cell |

|[pic] |
|Phytoplasma chromosome |

|Amino acid |
|Total content |
|Frequency |
|[%] |
| |
|A |
|9178 |
|4.51 |
| |
|C |
|2111 |
|1.04 |
| |
|D |
|9345 |
|4.59 |
| |
|E |
|12237 |
|6.02 |
| |
| |
|11568 |
|5.69 |
| |
|G |
|8641 |
|4.25 |
| |
|H |
|4193 |
|2.06 |
| |
|I |
|18032 |
|8.87 |
| |
|K |
|21932 |
|10.78 |
| |
|L |
|22045 |
|10.84 |
| |
|M |
|3784 |
|1.86 |
| |
|N |
|14390 |
|7.08 |
| |
|P |
|6638 |
|3.26 |
| |
|Q |
|11928 |
|5.86 |
| |
|R |
|5376 |
|2.64 |
| |
|S |
|11071 |
|5.44 |
| |
|T |
|11968 |
|5.88 |
| |
|V |
|9523 |
|4.68 |
| |
|W |
|1300 |
|0.64 |
| |
|X |
|2 |
|0.00 |
| |
|Y |
|8125 |
|3.99 |
| |
| |
|Aminoacid content of phytoplasma |

[pic]
Analysis of full-length proteins [fragments excluded]

Average protein length: 280 +/- 204 amino acid residues

Size range: 33 - 1571 amino acid residues