A colleague at Penn State, Dr. Surinder Chopra, has been working with near isogenic lines of sorghum for quite some time. Most of his research with sorghum has been to determine how specific flavonoid compounds are produced, where they are produced in the sorghum, and how they may help to defend the plant against stresses.
Recently, he has been drawn to determining how these compounds may be affected the below-ground, rhizosphere communities.
Recently, he has been drawn to determining how these compounds may be affected the below-ground, rhizosphere communities.
Specific questions that we are addressing include:
1. Are flavonoids exuded into the rhizosphere of sorghum having an impact on the rhizosphere microbial communities?
Wild type sorghum produces a specific flavonoid in the above-ground portion of the plant. This compound has been shown to have anti-fungal properties, thus is referred to as a phytoalexin. Recently, that flavonoid compound has also been found to be produced in the root and exuded into the rhizosphere. Since the compound has anti-fungal properties in the aboveground portion of the plant, it is hypothesized that it will also have an impact on the microbial communities in the rhizosphere.
2. Does a stress event lead to an increase in flavonoid production in the rhizosphere?
Previous studies have shown that flavonoid production from sorghum increases with stress. Stresses can be both biotic and abiotic. Biotic stresses include herbivory or fungal pathogen establishment, while abiotic stresses include drought, pH, freezing, etc. For the purposes of our field study, we considered how freezing would impact the production of flavonoids from the sorghum lines that we were growing.
3. How does a stress event (increased flavonoid production) impact microbial communities?
If flavonoids impact microbial communities and flavonoid production is increased after freezing, then it follows that the change to microbial communities would be amplified after a freezing event. Thus, we collected rhizosphere soil samples after a freezing event to determine how the microbial communities related to those before freezing.
4. Are there specific organisms that correlate with flavonoid production?
It is estimated that 90% of bacteria in soils are dormant. An estimated 40% of DNA in soils could be relic, meaning that the DNA is no longer encased in a cell and has been sorbed onto soil or organics. When we think about microbial communities and assessing changes to them via DNA sequencing, we should also keep in mind how prevalant dormancy and relic DNA are in the soil. As such, it stands to reason that only a small proportion of the microbial communities will be responsive to carbon exudation. Therefore, we are trying to determine what microbes are most responsive to flavonoid production and may be useful for down-stream analyses to assess sorghum responses to stress.
Wild type sorghum produces a specific flavonoid in the above-ground portion of the plant. This compound has been shown to have anti-fungal properties, thus is referred to as a phytoalexin. Recently, that flavonoid compound has also been found to be produced in the root and exuded into the rhizosphere. Since the compound has anti-fungal properties in the aboveground portion of the plant, it is hypothesized that it will also have an impact on the microbial communities in the rhizosphere.
2. Does a stress event lead to an increase in flavonoid production in the rhizosphere?
Previous studies have shown that flavonoid production from sorghum increases with stress. Stresses can be both biotic and abiotic. Biotic stresses include herbivory or fungal pathogen establishment, while abiotic stresses include drought, pH, freezing, etc. For the purposes of our field study, we considered how freezing would impact the production of flavonoids from the sorghum lines that we were growing.
3. How does a stress event (increased flavonoid production) impact microbial communities?
If flavonoids impact microbial communities and flavonoid production is increased after freezing, then it follows that the change to microbial communities would be amplified after a freezing event. Thus, we collected rhizosphere soil samples after a freezing event to determine how the microbial communities related to those before freezing.
4. Are there specific organisms that correlate with flavonoid production?
It is estimated that 90% of bacteria in soils are dormant. An estimated 40% of DNA in soils could be relic, meaning that the DNA is no longer encased in a cell and has been sorbed onto soil or organics. When we think about microbial communities and assessing changes to them via DNA sequencing, we should also keep in mind how prevalant dormancy and relic DNA are in the soil. As such, it stands to reason that only a small proportion of the microbial communities will be responsive to carbon exudation. Therefore, we are trying to determine what microbes are most responsive to flavonoid production and may be useful for down-stream analyses to assess sorghum responses to stress.
