Volume 31 Issue 8 - April 27, 2018 PDF
Plant and Microbes- Relationship of pros and cons
Hsin‐Yi Chen1, Jung‐Hyun Huh3, Ya‐Chi Yu1, Li‐Hsuan Ho1, Li‐Qing Chen2, Dorothea Tholl3, Wolf B. Frommer2, and Woei-Jiun Guo1,*
1 Department of Biotechnology and Bioindustry Sciences, Institute of Tropical Plant Science, National Cheng Kung University
2 Department of Plant Biology, Carnegie Institution for Science, USA
3 Department of Biological Sciences, Virginia Polytechnic Institute and State University, USA
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【106 Ta-You Wu Memorial Award】Special Issue

Most plants require soils for maximum growth. Therefore, plants will need to compete nutrients with soil microorganisms. However, plants also develop the mutualistic symbiotic relationship with microorganisms for optimal growth. During symbiosis, plants will secret carbohydrates, especially metabolic sources-sugars, to exchange inorganic minerals with mutualistic microorganisms[1]. However, pathogens could also hijack secreted sugars for propagation and infection that results in yield loss of crops. Thus, regulation for sugar efflux may determine the interaction between plant and microorganisms. In 2010, the hypothesis is supported by studies of the novel SWEET sugar facilitator family that function as sugar exporters and co-evolve with leaf pathogen[2]. Vacuoles are the major compartment to store sugars in plant cells and probably be the major source for sugar secretion. Possibly, SWEET proteins expressed in root vacuoles may module the interaction between roots and soil microbes. Indeed, our recent studies showed that Arabidopsis SWEET2 proteins function on root vacuoles and their expression was highly induced in roots by Pythium infection. Results showed that under normal growth conditions, AtSWEET2 functions as an importer to modulate sugar levels secreted from vacuoles to the cytoplasm. Upon pathogen, Pythium, infection, the expression of AtSWEET2 was induced to retrieve sugars from the cytosol to prevent sugar losses and further propagation of Pythium propagation. Loss of function in SWEET2 transport resulted in more sugar secretion from roots into rhizosphere and thus promoted Pythium propagation and infection. The study is the first time to discover the regulation mechanism of root sugar secretion which was demonstrated to modulate the interaction between roots and soil microorganisms. In the future, we may deploy the cultivation methods to control root sugar secretion so as to prevent pathogen infection in an environmental friendly approach.    

Working model of AtSWEET2 gene

  1. Kuhn C and Grof CPL (2010) Current Opinion in Plant Biology 13: 287-297
  2. Chen LQ Nature 468: 527-532
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