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Transgenic Citrus Expressing an Arabidopsis NPR1 Gene Exhibit Enhanced Resistance against Huanglongbing (HLB; Citrus Greening).

Dutt M, Barthe G, Irey M, Grosser J - PLoS ONE (2015)

Bottom Line: Overexpression of AtNPR1 resulted in trees with normal phenotypes that exhibited enhanced resistance to HLB.Phloem specific expression of NPR1 was equally effective for enhancing disease resistance.Transgenic trees exhibited reduced diseased severity and a few lines remained disease-free even after 36 months of planting in a high-disease pressure field site.

View Article: PubMed Central - PubMed

Affiliation: Citrus Research and Education Center, University of Florida, Lake Alfred, Florida, United States of America.

ABSTRACT
Commercial sweet orange cultivars lack resistance to Huanglongbing (HLB), a serious phloem limited bacterial disease that is usually fatal. In order to develop sustained disease resistance to HLB, transgenic sweet orange cultivars 'Hamlin' and 'Valencia' expressing an Arabidopsis thaliana NPR1 gene under the control of a constitutive CaMV 35S promoter or a phloem specific Arabidopsis SUC2 (AtSUC2) promoter were produced. Overexpression of AtNPR1 resulted in trees with normal phenotypes that exhibited enhanced resistance to HLB. Phloem specific expression of NPR1 was equally effective for enhancing disease resistance. Transgenic trees exhibited reduced diseased severity and a few lines remained disease-free even after 36 months of planting in a high-disease pressure field site. Expression of the NPR1 gene induced expression of several native genes involved in the plant defense signaling pathways. The AtNPR1 gene being plant derived can serve as a component for the development of an all plant T-DNA derived consumer friendly GM tree.

No MeSH data available.


Related in: MedlinePlus

A) A set of transgenic trees with the AtNPR1 construct, B) Close-up of an HLB positive transgenic tree with the AtNPR1 construct, C) A heavily infected HLB positive control tree, D) 2 feet spacing between two adjacent trees in our field plot. Normal citrus trees are usually planted at an 8 feet spacing or more, E) Close-up of a healthy flush, F) Close-up of an HLB infected leaf.
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pone.0137134.g003: A) A set of transgenic trees with the AtNPR1 construct, B) Close-up of an HLB positive transgenic tree with the AtNPR1 construct, C) A heavily infected HLB positive control tree, D) 2 feet spacing between two adjacent trees in our field plot. Normal citrus trees are usually planted at an 8 feet spacing or more, E) Close-up of a healthy flush, F) Close-up of an HLB infected leaf.

Mentions: Disease resistance to HLB in this study was evaluated in two ways. First, in a no-choice greenhouse evaluation study, 3 replicated clones of independent transgenic plant lines were exposed to free flying CLas positive ACP continuously for two years. Trees were routinely pruned and fertilized with both 9 month slow release and liquid fertilizer to stimulate new flush production. These trees were evaluated every 6 months for two years for the presence of HLB by qPCR as outlined before. ACP were also randomly evaluated during this study for the presence of the CLas. In the second concurrent study, selected transgenic trees and controls (consisting of 10% of the total tree population) were planted in a high disease pressure (over 90% infection rate) field site in a randomized block design experiment. In our test site, trees were planted at a narrow spacing of 2 feet to maximize land utilization (Fig 3D). These trees were similarly evaluated every 6 months for three years by qPCR for the presence of HLB. Data were analyzed to calculate standard error using MS Excel.


Transgenic Citrus Expressing an Arabidopsis NPR1 Gene Exhibit Enhanced Resistance against Huanglongbing (HLB; Citrus Greening).

Dutt M, Barthe G, Irey M, Grosser J - PLoS ONE (2015)

A) A set of transgenic trees with the AtNPR1 construct, B) Close-up of an HLB positive transgenic tree with the AtNPR1 construct, C) A heavily infected HLB positive control tree, D) 2 feet spacing between two adjacent trees in our field plot. Normal citrus trees are usually planted at an 8 feet spacing or more, E) Close-up of a healthy flush, F) Close-up of an HLB infected leaf.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4580634&req=5

pone.0137134.g003: A) A set of transgenic trees with the AtNPR1 construct, B) Close-up of an HLB positive transgenic tree with the AtNPR1 construct, C) A heavily infected HLB positive control tree, D) 2 feet spacing between two adjacent trees in our field plot. Normal citrus trees are usually planted at an 8 feet spacing or more, E) Close-up of a healthy flush, F) Close-up of an HLB infected leaf.
Mentions: Disease resistance to HLB in this study was evaluated in two ways. First, in a no-choice greenhouse evaluation study, 3 replicated clones of independent transgenic plant lines were exposed to free flying CLas positive ACP continuously for two years. Trees were routinely pruned and fertilized with both 9 month slow release and liquid fertilizer to stimulate new flush production. These trees were evaluated every 6 months for two years for the presence of HLB by qPCR as outlined before. ACP were also randomly evaluated during this study for the presence of the CLas. In the second concurrent study, selected transgenic trees and controls (consisting of 10% of the total tree population) were planted in a high disease pressure (over 90% infection rate) field site in a randomized block design experiment. In our test site, trees were planted at a narrow spacing of 2 feet to maximize land utilization (Fig 3D). These trees were similarly evaluated every 6 months for three years by qPCR for the presence of HLB. Data were analyzed to calculate standard error using MS Excel.

Bottom Line: Overexpression of AtNPR1 resulted in trees with normal phenotypes that exhibited enhanced resistance to HLB.Phloem specific expression of NPR1 was equally effective for enhancing disease resistance.Transgenic trees exhibited reduced diseased severity and a few lines remained disease-free even after 36 months of planting in a high-disease pressure field site.

View Article: PubMed Central - PubMed

Affiliation: Citrus Research and Education Center, University of Florida, Lake Alfred, Florida, United States of America.

ABSTRACT
Commercial sweet orange cultivars lack resistance to Huanglongbing (HLB), a serious phloem limited bacterial disease that is usually fatal. In order to develop sustained disease resistance to HLB, transgenic sweet orange cultivars 'Hamlin' and 'Valencia' expressing an Arabidopsis thaliana NPR1 gene under the control of a constitutive CaMV 35S promoter or a phloem specific Arabidopsis SUC2 (AtSUC2) promoter were produced. Overexpression of AtNPR1 resulted in trees with normal phenotypes that exhibited enhanced resistance to HLB. Phloem specific expression of NPR1 was equally effective for enhancing disease resistance. Transgenic trees exhibited reduced diseased severity and a few lines remained disease-free even after 36 months of planting in a high-disease pressure field site. Expression of the NPR1 gene induced expression of several native genes involved in the plant defense signaling pathways. The AtNPR1 gene being plant derived can serve as a component for the development of an all plant T-DNA derived consumer friendly GM tree.

No MeSH data available.


Related in: MedlinePlus