All Articles by Tim Morton

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All Articles by Tim Morton

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All Articles by Tim Morton

I am broadly interested in the evolution and structure of host-associated microbial communities. Of the numerous taxa that compose the Arabidopsis microbiome, fungi make up a substantial portion, but studies to date have tended to focus on the bacterial portion. With the help of my labmate Manon Guilberteau, I have cultured over thirty unique fungal species from natural populations of Arabidopsis. By infecting sterile Arabidopsis with specific microbial taxa under tightly controlled environmental conditions, I will investigate the role of fungi in formation of the non-mycorrhizal plant microbiome.

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All Articles by Tim Morton

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All Articles by Tim Morton

I am a phytopathologist in Sichuan Agricultural University, China. My research is mainly focused on the interaction mechanisms between rice fungal pathogens and hosts. I have worked on the cytology, morphology, histologic pathology, genomics and epidemiology of rice sheath blight and kernel smut disease pathogens, and illustrated the effectors and evolution mechanism against hosts. A second line of research deals with defenses against Lepidoptera, Homoptera and nematode pests. We clone plant defensive genes, do functional verification, create transgenic crops but we are also interested in the genomics of Bacillus thuringiensis, a Gram-positive bacteria that often is used as a biological pesticide. In the Bergelson lab, I am investigating the fitness of Pseudomonas syringae among different crops. Pseudomonas syringae is multi host generalist pathogen, it can infect more than 100 families plants. It has a complex life history, including pathogenic, epiphytic and saprophytic phases. The mechanisms of pathogen virulence and host resistance have been well characterized in several model systems. But knowledge about genetic dynamics in ecology is limited. Tn-seq high-throughput parallel sequencing will be used to elucidate the fitness mechanism of Pseudomonas syringae in crops. One can find me in the following website: https://www.researchgate.net/profile/Aiping_Zheng2 http://scholar.google.com/citations?hl=en&user=98cgrigAAAAJ&sortby=pubdate&view_op=list_works and http://wiki.pestinfo.org/wiki/Aiping_Zheng. Selected Publications Lei D, Lin R, Yin C, Li P, Zheng A. Global protein-protein interaction network of rice sheath blight pathogen. J Proteome Res. 2014 Jul 3;13(7):3277-93. doi: 10.1021/pr500069r. Aiping Zheng, Runmao Lin, Danhua Zhang, etc. The evolution and pathogenic mechanisms of the rice sheath blight pathogen. Nature Communications. 2013, 4: 1424 doi:10.1038/ncomms2427. Li S, Li W, Huang B, Cao X, Deng Q, Wang S, Zheng A, Zhu J, Liu H, Wang L, Li P. Natural variation in PTB1 regulates rice seed setting rate by controlling pollen tube growth. Nature Communications. 2013, 4:2793. doi: 10.1038/ncomms3793. Guan P, Ai P, Dai X, Zhang J, Xu L, Deng Q, Li S, Wang S, Liu H, Wang L, Li P, Zheng A. Complete genome sequence of Bacillus thuringiensis serovar Sichuansis strain MC28. J Bacteriol. 2012 Dec;194(24):6975. doi: 10.1128/JB.01861-12.

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All Articles by Tim Morton

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All Articles by Tim Morton

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All Articles by Tim Morton

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All Articles by Tim Morton

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Recent Publication: Genetic architecture & pleiotropy shape costs of Rps2-mediated resistance in A. thaliana

In prior studies, our lab found that costs of resistance to pathogens in the absence of disease was ~5-10% for the resistance (R) genes Rps5 and Rpm1, respectively. However, Arabidopsis thaliana has 149 R-genes so it is unlikely that many R genes incur such a high cost. The now published research of former PhD student Alice MacQueen focuses on Rps2 that exists as an ancient balanced polymorphism with two long-lived clades of alleles. Alice conducted field trials that show that Arabidopsis thaliana plants with resistant Rps2 are no less fit than those with a susceptible Rps2 allele in the absence of disease. Both resistant and susceptible Rps2 alleles contribute to controlling defense and stress gene expression thus presenting a pleiotropic effect to explain the maintenance of both alleles.

We are excited that Ana-Lisa Laine reviews the significance of Alice’s work in
Disease resistance: Not so costly after all:

“These results demonstrate how profoundly the magnitude of fitness costs associated with disease resistance may be shaped by genomic architecture and pleiotropy… These findings shed much-needed light on how the full repertoire of R genes is maintained in the A. thaliana genome. More broadly, these results show that the nature of fitness costs and trade-offs of disease resistance vary among loci even within the same host. Such information is crucial for crop breeding, where the challenge lies in producing high-yield crops while minimizing the cost of disease control.”

We illustrated this post with Sir John Tenniel’s drawing of the Red Queen and Alice from Lewis Carroll’s Through the Looking-Glass. The Red Queen tells Alice: “Now, here, you see, it takes all the running you can do, to keep in the same place”. This is commonly used as an analogy for co-evolution, as hosts and parasites have to rapidly adapt to each other in order to not loose the race. A concept introduced by Leigh Van Valen’s 1973 article. The rate of this co-evolutionary arms race is expected to be constrained by fitness costs.

Alice MacQueen performed fitness experiments as part of her doctoral dissertation and is now a post doctoral researcher with the Juenger lab in Austin Texas.

Xiaoqin Sun worked with the Bergelson lab from 2007-2009 and is now at the Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing.