L8- cause dis toxins

Question 1

2 types of toxin based on apparent role in pathogenicity, these are

Answer 1

1. Host-Selective Toxins - plants which are susceptible to the disease are sensitive to the toxin. thought that sensitivity to the toxin therefore causes the disease
2. NON-host selective toxins
   plants which arent attacked by pathogen can be sensitive to the toxin

Question 2

example genus which contains many host selective toxins

Answer 2

Bipolaris (ascomycete fungi)

Question 3

genetic study ……. confirmed link between host range and ………. ………

Answer 3

1960

host range and sensitivity to fungi

Question 4

Bipolaris victoriae causes

produces toxin:

Answer 4

Bipolaris victoriae causes victoria blight on oats with PC-2 resistance gene

victorin toxin

Question 5

Bipolaris zeicola causes

produces toxin:

Answer 5

Bipolaris zeicola causes Maize leaf spot + ear mould

HC toxin

Question 6

what two species were crossed in 1960 with what results

Answer 6

Bipolaris victoriae and Bipolaris zeicola
phylogeny 4
1. victorin on sensitive oats
2. HC on sensitive maize 
3. BOTH
4. Neither

confirmed toxin and disease correlate 1:1 correspondance bt pathogen + disease

Question 7

what causes sensitivity to Bipolaris zeicola and others insensitive?

Host-selective toxin

Answer 7

Maize has loss of the Hm1 gene

Hm1 gene found in many cereal species. Hm1 reduces HC toxin - detoxifies it therefore is resistant

Tested - silenced gene in resistant Barley = now sensitive

Question 8

Bipolaris zeicola how does the toxin work

Answer 8

Bipolaris zeicola Race 1 produces HC toxin
HC toxin - cyclic peptide
inhibits histone deacetylase
(inhibits gene expression regulation)

Question 9

BmT toxin is produced by?

Answer 9

Bipolaris maydis

Question 10

BmT is only sensitive to what race

how?

Answer 10

Race T Maize not Race O
Race T - texas male sterile cytoplasm, has the Cms-T gene

Bmt bind to TURF13/URF13 protein in the inner membrane of mitochondira - only present in cms-T strains!!! TURF13+Bmt = channel in membrane

protein encoded for in mt - gene is evolutionary novelty.

Question 11

Bmt toxin led to

Answer 11

the most serious maize disease epidemic in recent history 1970

Question 12

toxins work in different ways to make them susceptible for HC toxin 1. and for BmT toxin 2.

Answer 12

1. unable to degrade - loss of gene

2. presence of binding site

Question 13

Biosynthesis of toxins often include

Answer 13

multifunctional enzymes

Question 14

Production of HC toxin uses what enzyme

Answer 14

non-ribosomal peptide synthase encoded for of HSt1 gene

orthologs of this gene have been found

Question 15

Production of BmT toxin uses what enzyme

Answer 15

polyketide synthase

homologs on Tox1 locus which contain BmT synthesis gene have been found Condon 2018

Question 16

Other host-selective toxins have been identified ….

1. toxin
2. causes
3. from what sp
4. reference

Answer 16

1. SV toxins
2. Causing Brown Spot of European Pear in Japan
3. Stemphylium sp
4. 2017 Tanahashi

found that Stemphylium sp in Japan produce the same toxins as S. vesicarium in Europe

Question 17

Brown spot of european pear is caused by

Answer 17

Stemphylium sp

Question 18

brown spot of european pear caused by what toxins

these toxins also produced where

Answer 18

SV toxins

Stemphylium vesicarium