Leaves of thale cress protect the plant from pathogenic microorganisms by interrupting the cellular signals that otherwise keep the stoma open and vulnerable to bacterial invasion.

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Plants rely on complex innate immune systems to make up for their lack of adaptive systems. They use complex signaling cascades that can detect and respond to bacterial and fungal pathogens both inside and outside their cells. One type of response is for the plant to close their stoma--the small openings on its leaves--which denies the pathogen entry points into the plant. The RIN4 protein has recently been shown to be instrumental in this process. Under normal circumstances, proteins embedded in the cell membrane send signals to RIN4 to keep stoma opened. When chemical signals from pathogenic microbes are detected, these signals stop and the stoma close.

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"Unlike vertebrates, plants lack an adaptive immune system and rely on their innate immune system to recognize and restrict pathogenic microbes...[one form] uses intracellular plant resistance (R) proteins to recognize pathogen effectors delivered inside host cells during infection, resulting in effector-triggered immunity (ETI)...RIN4 (At3g25070) is the only known protein that can regulate both branches of the plant immune system...Arabidopsis protein RIN4 functions with the PM H+-ATPase to regulate stomatal apertures, inhibiting the entry of bacterial pathogens into the plant leaf during infection." (Liu et al. 2009:1)

"Bacterial pathogens gain entry inside plant leaves through wounds or natural openings like stomata...A pair of guard cells surrounds stomatal pores. Guard cells respond to diverse stimuli in order to regulate stomatal apertures...stomatal closure is induced...in an attempt to restrict bacterial invasion." (Liu et al. 2009:2)

"RIN4 protein acts in concert with PM H+-ATPases to regulate stomatal apertures...Importantly, the RIN4 knockout line does not re-open its stomata in response to virulent Pst." (Liu et al. 2009:10)

RIN4 functions with plasma membrane H+-ATPases to regulate stomatal apertures during pathogen attack

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Thale CressArabidopsis thalianaSpecies

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