How fungi acquire sugar from plants


World population is constantly increasing and food demands to cope with it will have to as well soon. If the trend continues as predicted by 2050 the world food production will need to double to cope with the increasing growing human population [2]. Will we be able to cope with it?

Well it seems that there are some factors that may have an influence on our future predictions, one of them being the creation of a sustainable intensification of world agriculture, as we saw in the System of Rice Intensification (SRI), supported by research and studies that will focus on increasing current productivity of crops by all possible means, including technological innovations and a better understanding of how plant diseases can be better fought and controlled. 

One of the factors that negatively influences crop production are indeed plant diseases. Between 10 and 30% of the global harvest is lost as a consequence of plant diseases [1], a risk that is becoming a threat to global food security [2]. But understanding the biology of plant infection by disease-causing agents, such as viruses, bacteria, and fungi is not simple.  Image: See credits under ref. [4] below.



In that line, a study from N.J. Talbot shows how one of the two types of fungal pathogens, the biotrophs, is able to acquire sugar from living plant cells without stimulating the plant defense mechanism, making them able to spread without killing their host, something that it is common for the other type of fungal pathogens, the necrotrophs [2]. Biotrophs are the cause of the most pervasive plant diseases as powdery mildew of barley caused by Blumeria graminis for instance [2].   

In order to grow, a plant pathogenic fungus must secure an organic carbon source from the plant. Now a study published in this issue of PLoS Biology [3] shows how sucrose, which constitutes the most abundant storage sugar within plants and the product of photosynthesis, is directly utilized by invading pathogens without the need for its extracellular degradation by fungal secreted invertases [2], showing also possible lines of study towards new mechanisms of enhancing plant defense against fungal pathogen attacks, another way to increase crop production. 



[1] Strange R. N, Scott P. R (2005) Plant disease: a threat to global food security. Annu Rev Phytopathol 43: 83–116.
[2] Talbot NJ (2010) Living the Sweet Life: How Does a Plant Pathogenic Fungus Acquire Sugar from Plants? PLoS Biol 8(2): e1000308. doi:10.1371/journal.pbio.1000308
[3] Wahl R, Wippel K, Goos S, Kämper J, Sauer N (2010) A novel high-affinity sucrose transporter is required for virulence of the plant pathogen Ustilago maydis. PLoS Biol 8(2): e1000303. doi:10.1371/journal.pbio.1000303.
[4] Pixabay image under Public Domain License CC0 1.0 Universal (CC0 1.0).