Recipient Organization
UNIVERSITY OF GEORGIA
200 D.W. BROOKS DR
ATHENS,GA 30602-5016
Performing Department
(N/A)
Non Technical Summary
For decades, a serious cotton disease called Cotton Bacterial Blight (CBB) played a game of cat-and-mouse with farmers and scientists. Every time new disease-resistant cotton varieties were developed, the bacteria behind CBB found a way to fight back.However, apowerful resistance gene in cotton, known as B12, has successfully held off all known versions of the CBB-causing bacteria for decades. That's unusual, since most resistance traits eventually stop working. The goal of this project isto figure out what makes B12 so unusually stable and how we can use that knowledge toprotect this important and valuable toolagainst CBB and potentially develop long lasting resistance against other plant diseases.We plan to test different bacterial genes to see which ones trigger B12's immune response in cotton. This could not only reveal why B12 is so effective, but also help scientists watch for signs the bacteria might be changing again. Because chemical treatments for CBB don't work well, staying ahead of the disease genetically is key to keeping cotton crops, and its significanteconomic contributions, safe.
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
The rapid reemergence of Xcm during the 2010's outbreaks provided a warning shot as well as the opportunity to prepare. Xcm has shown that it can rapidly reestablish itself as a pest of concern when the opportunity presents. Between 2015 and 2017 CBB was estimated to cause $4.2M in losses in Georgia alone. The dominant B12 resistance locus against CBB is broadly distributed among cotton cultivars and confers resistance to Xcm race 18 in both modern elite and historic cotton cultivars. Determining the mechanisms underlying the longevity and stability of B12 resistance will provide crucial insights towards preservation of this critical management tool. How B12-mediated resistance has maintained the upper hand in the perpetual arms race between pathogens and plants (and plant breeders) is unknown. To gain insight into how B12 resistance has won this battle in the evolutionary arms race, and to apply those insights towards deployment of stable resistance against other cotton pathogens, it is crucial to identify the type III effector genes of Xcm that facilitate B12 recognition and avirulence.To identify the Xcm T3E(s) recognized by the B12 resistance locus and gain insights into the mechanisms for disease resistance stability and longevity we propose the following two research objectives. Completion of these objective will have both direct and indirect benefits for cotton and CBB research and help safeguard against CBB in the future.Objective 1: Clone a comprehensive set of T3E genes from a race 18 Xcm strain into a purpose-developed AMTE HR-cell death RUBY reporter vector.Objective 2: Identify Xcm T3Es recognized in B12 CBB-resistant cotton and assess their contributions to cotton virulence and avirulence.
Project Methods
Objective 1: Clone a comprehensive set of T3E genes from a modern race 18 Xcm strain into a purpose-developed AMTE HR cell death RUBY reporter vector. We will develop the genetic infrastructure to facilitate identification of B12-recognized type III effectors as well as other avr genes recognized via dominant resistance genes in cotton via Agrobacterium-mediated transient expression (AMTE). Specifically, we will A) clone the set of non-TAL and TAL type III effectors from a sequenced Xcm race 18 strain; and B) develop an AMTE vector for visual screening of the hypersensitive response cell death with RUBY co-expression providing a robust internal control.Objective 2: Identify Xcm T3Es recognized in B12 CBB-resistant cotton and assess their contributions to virulence and avirulence. In Objective 2 we will generate a pRUBYGate T3E expression library and use AMTE to identifyT3Es conferring B12-dependent cell death in cotton cotyledons. We will also use mutational analysis in Xcm to determine the roles of B12-recognized T3Es in both Xcm virulence and B12-mediated avirulence.