Research Square (Research Square), Feb 6, 2023
Excess cellular sterol is harmful in mammals and plants, but the mechanisms why are awaiting clar... more Excess cellular sterol is harmful in mammals and plants, but the mechanisms why are awaiting clari cation. Here we nd a strong autoimmune response to be associated to excess endoplasmic reticulum (ER) sterols. This was obtained by studying a plant peroxisome lipase, SSD5, required for the lesion phenotype of the Arabidopsis syntaxin mutant, pen1 syp122. SSD5 is a lipase with a catalytic triad including a GxSxG motif localized to a subdomain of the peroxisome periphery. Lipidomics revealed reduced steryl ester levels in pen1 syp122 when SSD5 is mutated. This involvement in sterol homeostasis was con rmed by a requirement of SSD5 for the lesions of hise1 psat1 that suffers from excess ER sterol. These data suggest SSD5 is contributing to a peroxisome-located segment of the sterol biosynthesis pathway. SSD5's contribution to the pen1 syp122 autoimmunity is not associated with nine highly diverse downstream immune components, and SSD5 does not in uence general plant disease levels and immunity. Therefore, our data indicated SSD5 as well as ER sterol functions upstream of immune activation. This in turn suggests plant excess ER sterol to activate one or more immune receptors.
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Papers by Wenjun Xie