Farnesylation-mediated control of skotomorphogenesis and seedling establishment in Arabidopsis thaliana

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Skotomorphogenesis is growth in the dark, a critical process in the establishment of seedlings for all crop systems in which the seed is sown below the soil surface. Regulation of skotomorphogenesis, seedling growth, plant development, and stress tolerance has been shown to involve the interplay and negative interactions between the signalling and synthesis of the stress hormone abscisic acid (ABA) and the growth hormone brassinosteroid (BR). Mutations or modifications resulting in reduced BR synthesis have been shown to enhance perception of ABA for improved stress responses and overall drought tolerance. A previous study demonstrated that the farnesyltransferase, Enhanced Response to ABA 1 (ERA1), is required for BR synthesis through farnesylation of the terminal enzyme of the BR biosynthesis pathway. However, new evidence suggests that the absence of ERA1 can directly impact the BR-dependent skotomorphogenic response as farnesylation may be important in the activity of downstream genes associated with BR-induced signalling. Screening BR-regulated gene expression for potential substrates for farnesylation has yielded three likely candidate proteins: a bHLH-type transcription factor of the Phytochrome-Interacting Factor (PIF) group, PIF3; and a pair of cell-wall modification enzymes of the Xyloglucan endotransglycosylase/hydrolase (XTH) family, XTH22 and XTH23. Complementation experiments revealed that PIF3 lacking farnesylation was unable to rescue the skotomorphogenic defects observed in the multigenic pifq mutant background. PIF3 farnesylation was further shown to be required for transcriptional activity of PIF3 in the transgenic seedling. This study has directly linked PIF3 farnesylation with transcriptional control during skotomorphogenesis. Additional experiments highlighted the complexity of farnesylation-mediated regulation among downstream effectors. Methods and tools developed in this study can be used to verify additional targets responsible for the impact of farnesylation on seedling growth.
Farnesylation, Skotomorphogenesis, Brassinosteroid, Seedling Establishment, CRISPR-Cas9, Plant Developmental Biology
Hickerson, N. M. (2024). Farnesylation-mediated control of skotomorphogenesis and seedling establishment in Arabidopsis thaliana (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.