Abstract
The role if any that host metabolism plays in plant immunity remains an open question. Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1), a pathogen that causes a lethal leaf blight disease, seems to provide an interesting glimpse into this question. CCR1 causes disease by using a cyclic tetrapeptide that has been named HC-toxin. This virulence action is countered by the disease resistance gene Hm1 that inactivates HC-toxin by encoding an NADPH-dependent reductase (HCTR). Resistance conferred by Hm1 is absolute and operates in every part of the plant. In contrast, an allele of Hm1 (Hm1A) confers protection only at maturity and not at the seedling stage. The HCTR encoded by Hm1A differs from the wild-type HCTR by five amino acid substitutions, which we predicted only weaken the activity of HCTR and not inactivate it completely. We used targeted mutagenesis with EMS to test this hypothesis. This procedure led to the generation of two new alleles of Hm1 that, like Hm1A , conferred effective resistance to CCR1 only at maturity. These APR alleles of Hm1 were the result of single amino acid substitutions. In one allele the substitution was from Threonine to Methionine at residue 90 (T90M) and the other had a Valine to Methionine conversion at residue 210 (V210M). Five fully susceptible alleles were also found in this study, and they all had undergone drastic mutations such as the formation of premature stop codons. These results demonstrate that the APR alleles of Hm1 are the result of partial loss-of-function mutations of the gene. The question, of course, is why weak alleles behave of Hm1 fail to confer resistance in corn seedlings? One possibility is that it may have something to do with the fluctuating levels of NADPH (a cofactor for HCTR) in corn seedlings. Given that Hm1A seedlings become resistant to CCR1 when grown under extended photoperiod or in the presence of 3% sucrose, are consistent with our hypothesis. During our quest for the mechanistic basis of APR, we identified maize seedlings incubated in continuous dark for 48 hours turned susceptible to CCR1 Tox-, the non-toxin producing isolate. This loss of resistance is described as "DILI", dark-induced loss of immunity. Genetic studies revealed DILI is independent of Hm1 and CCR1 toxin producing ability. In addition to CCR1, Cochliobolus heterostrophus, Magnaporthe grisea and Colletotrichum graminicola were able to infect dark-incubated plants, showing that DILI is not pathogen specific. But what happens in dark that is making maize seedlings susceptible to different pathogens. One possibility could be loss of photosynthesis in the dark. Our results from DCMU herbicide which inhibits photosynthesis showed that loss of photosynthesis is responsible for DILI. Interestingly, by supplementing sugars DILI was suppressed, showing that starvation induced by loss of sugars is indeed responsible for DILI. Supporting these results, transcriptome analysis showed complete shut-down of metabolism. Fascinatingly, this is the first time we are showing a direct correlation between metabolism and immunity in the plant kingdom.
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Claims 16
Claim · model-written summary
The Hm1A allele protects maize from CCR1 only at maturity, not as seedlings.
- Organ / stage
- maturity and not at the seedling stagee0
- Interactor
- Cochliobolus carbonum race1
Bipolaris zeicolae1pathogen - Gene
- Hm1Ae0
- Outcome
- protectione0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“an allele of Hm1 (Hm1A) confers protection only at maturity and not at the seedling stage”
e1“in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
EMS mutagenesis produced two Hm1 alleles giving maize effective CCR1 resistance only at maturity.
- Interactor
- Cochliobolus carbonum race1Bipolaris zeicolae1pathogen
- Gene
- Hm1e0
- Outcome
- effective resistance to CCR1e0
- Value
- two new allelese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This procedure led to the generation of two new alleles of Hm1 that, like Hm1A , conferred effective resistance to CCR1 only at maturity”
e1“in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
One adult-resistance Hm1 allele had a threonine-to-methionine substitution at residue 90.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In one allele the substitution was from Threonine to Methionine at residue 90 (T90M)”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
The other adult-resistance Hm1 allele had a valine-to-methionine substitution at residue 210.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the other had a Valine to Methionine conversion at residue 210 (V210M)”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
Five fully susceptible Hm1 alleles had drastic mutations including premature stop codons.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Five fully susceptible alleles were also found in this study, and they all had undergone drastic mutations such as the formation of premature stop codons”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
Adult plant resistance alleles of Hm1 were partial loss-of-function mutations.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“These results demonstrate that the APR alleles of Hm1 are the result of partial loss-of-function mutations of the gene”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
An extended photoperiod made Hm1A maize seedlings resistant to CCR1.
- Material
- Hm1A seedlingse0
- Treatment
- extended photoperiode0
- Outcome
- resistant to CCR1e0
- Direction
- resistante0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hm1A seedlings become resistant to CCR1 when grown under extended photoperiod”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
Three percent sucrose made Hm1A maize seedlings resistant to CCR1.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hm1A seedlings become resistant to CCR1 when grown under extended photoperiod or in the presence of 3% sucrose”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
Continuous darkness for 48 hours made maize seedlings susceptible to a nontoxin-producing CCR1 isolate.
- Treatment
- continuous dark for 48 hourse0
- Interactor
- CCR1 Tox-e0pathogen
- Outcome
- susceptible to CCR1 Tox-e0
- Direction
- susceptiblee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize seedlings incubated in continuous dark for 48 hours turned susceptible to CCR1 Tox-, the non-toxin producing isolate”
Claim · model-written summary
Dark-induced loss of immunity was independent of Hm1 and CCR1 toxin production.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Genetic studies revealed DILI is independent of Hm1 and CCR1 toxin producing ability”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
Cochliobolus heterostrophus infected dark-incubated maize plants.
- Interactor
- Cochliobolus heterostrophus
Bipolaris maydise0pathogen - Outcome
- infect dark-incubated plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cochliobolus heterostrophus, Magnaporthe grisea and Colletotrichum graminicola were able to infect dark-incubated plants”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
Magnaporthe grisea infected dark-incubated maize plants.
- Interactor
- Magnaporthe grisea
Pyricularia griseae0pathogen - Outcome
- infect dark-incubated plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cochliobolus heterostrophus, Magnaporthe grisea and Colletotrichum graminicola were able to infect dark-incubated plants”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
Colletotrichum graminicola infected dark-incubated maize plants.
- Interactor
- Colletotrichum graminicola
_G.W._Wilson_1235209.jpg?width=60)
Colletotrichum graminicolae0pathogen - Outcome
- infect dark-incubated plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_G.W._Wilson_1235209.jpg?width=500)
Verbatim
e0“Cochliobolus heterostrophus, Magnaporthe grisea and Colletotrichum graminicola were able to infect dark-incubated plants”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
DCMU inhibition of photosynthesis indicated that loss of photosynthesis causes dark-induced loss of immunity.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Our results from DCMU herbicide which inhibits photosynthesis showed that loss of photosynthesis is responsible for DILI”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
Sugar supplementation suppressed dark-induced loss of immunity.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“by supplementing sugars DILI was suppressed”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
Claim · model-written summary
Transcriptome analysis showed a complete shutdown of metabolism during dark-induced loss of immunity.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transcriptome analysis showed complete shut-down of metabolism”
e1“Our research on adult plant resistance (APR) in maize to Cochliobolus carbonum race1 (CCR1)”
The same questions in other papers
sucrose · disease · Zea mays (maize)Positive and negative results
1 paper in the same direction as this paper · 2 in the opposite direction
- no effect
- negative
- positive
light · disease · Zea mays (maize)Positive and negative results
2 papers in the same direction as this paper · 4 in the opposite direction
- negative
- negative
- negative
3 papers more in this group
See all 7 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.