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Abel, S., Oeller, P.W. & Theologis, A. Early auxin-induced genes encode short-lived nuclear proteins PNAS USA 91, 326-330, (1994)
The plant growth hormone indoleacetic acid (IAA) transcriptionally activates gene expression in plants. Some of the genes whose expression is induced by IAA encode a family of proteins in pea (PS-IAA4 and PS-IAA6) and Arabidopsis (IAA1 and IAA2) that contain putative nuclear localization signals that direct a beta-glucuronidase reporter protein into the nucleus. Pulse-chase and immunoprecipitation experiments have defined the t1/2 of the PS-IAA4 and PS-IAA6 proteins to be 8 and 6 min, respectively. Their most prominent feature is the presence of a beta alpha alpha motif similar to the beta-sheet DNA-binding domain found in prokaryotic repressors of the Arc family. Based on these data, we suggest that plant tissues express short-lived nuclear proteins as a primary response to IAA. We propose that these proteins act as activators or repressors of genes responsible for mediating the various auxin responses.
Abel, S. & Theologis, A. Transient transformation of Arabidopsis leaf protoplasts: a versatile experimental system to study gene expression Plant Journal 5, 421-427, (1994)
An improved protocol is reported to isolate and transiently transform mesophyll protoplasts of Arabidopsis thaliana. Transfected leaf protoplasts support high levels of expression of the bacterial reporter gene coding for β-glucuronidase (GUS), under the control of the cauliflower mosaic virus (CaMV) 35S promoter. Transient expression of GUS activity was monitored spectrophotometrically and reached a maximum between 18 and 48 h after polyethylene glycol (PEG)-mediated DNA uptake. Histochemical staining for GUS activity revealed reproducible transformation frequencies between 40 and 60%, based on the number of protoplasts survived. To demonstrate the applicability of the transient expression system, the subcellular localization of GUS proteins tagged with different nuclear polypeptides was studied in transfected mesophyll protoplasts, revealing nuclear compartmentalization of the chimeric GUS enzymes. Furthermore, Arabidopsis mesophyll protoplasts support auxin-mediated induction of chloramphenicol acetyl-transferase (CAT) activity when transfected with a transcriptional fusion between the CAT reporter gene and the early auxin-inducible PS-IAA4/5 promoter. Hence, the method allows in vivo analysis of promoter activity and subcellular localization of fusion proteins in a homologous transformation system.