Starving the enemy: how plant and microbe compete for sugar on the border

Abstract

As the primary energy source for a plant host and microbe to sustain life, sugar is generally exported by Sugars Will Eventually be Exported Transporters (SWEETs) to the host extracellular spaces or the apoplast. There, the host and microbes compete for hexose, sucrose, and other important nutrients. The host and microbial monosaccharide transporters (MSTs) and sucrose transporters (SUTs) play a key role in the “evolutionary arms race”. The result of this competition hinges on the proportion of sugar distribution between the host and microbes. In some plants (such as Arabidopsis, corn, and rice) and their interacting pathogens, the key transporters responsible for sugar competition have been identified. However, the regulatory mechanisms of sugar transporters, especially in the microbes require further investigation. Here, the key transporters that are responsible for the sugar competition in the host and pathogen have been identified and the regulatory mechanisms of the sugar transport have been briefly analyzed. These data are of great significance to the increase of the sugar distribution in plants for improvement in the yield.

Cellooligomer/CELLOOLIGOMER RECEPTOR KINASE1 Signaling Exhibits Crosstalk with PAMP-Triggered Immune Responses and Sugar Metabolism in Arabidopsis Roots

“…Crosstalk between sugar transport and innate immunity or stress responses is well documented [ 13 , 35 ]. SWEET and STP transporters enhance or restrict disease through controlling the level of nutrients provided to pathogens [ 35 ].…”

“…It is believed that most of the degradation products are utilized for cell wall regeneration [ 33 ]; however, it is also possible that some of them are integrated into the primary sugar metabolism and serve as an energy source. The availability of reduced carbon also impacts the growth of the symbiotic and pathogenic microorganism associated with the hosts [ 13 , 33 ]. SUGAR TRANSPORTER PROTEINs (STPs) are proton-coupled symporters responsible for the uptake of glucose from the apoplast into plant cells, where they function as key signaling molecules and play a vital role in plant responses to stressors such as dehydration and prevalent fungal infections [ 34 , 35 ].…”

The link between changing in host carbon allocation and resistance to Magnaporthe oryzae : a possible tactic for mitigating the rice blast fungus

“…Controlling the host carbon supply may be one of a viable tactic to lessen blast severity because M. oryzae is a hemibiotrophic pathogen that requires sugar during the early infection process. 25 Nevertheless, the connection between the change in host carbon source and the growth of M. oryzae infection has not been thoroughly investigated in research.…”

“… 34 Also, understanding the dynamics of carbon allocation will aid in the breeding of crop varieties tolerant to disease and maximize resource utilization for increased resilience. 23 , 25

Figure 1. The possible strategy for controlling rice blast disease is through regulation of the carbon allocation of the host plant.

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“…Sugar transporters located in the plasma membrane are involved in this process. 25 , 47 However, microbes are so clever that they can use the host sugar transporter to their advantage and export sugar from the cell. Knowing this mechanism could lead to a viable, long-term plan to stop different microbes from spreading to other plants.…”