Protein phosphatase activity is required for light-inducible gene expression in maize.

Abstract

Chlorophyll accumulation and photosynthetic gene activation are two hallmarks of greening process in etiolated maize leaves in response to light signals. However, very little is known about the relevant signal transduction pathways mediating these essential processes that lead to photosynthetic competence. It is shown here that a potent and specific protein phosphatase 1 (PP1) and PP2A inhibitor, okadaic acid, efficiently blocks chlorophyll accumulation induced by light in etiolated maize leaves. In addition, the light‐inducible expression of two photosynthetic fusion genes can be specifically suppressed by the structurally unrelated PP1 and PP2A inhibitors, okadaic acid and calyculin A, using a sensitive and physiological maize protoplast transient assay. The specificity and effective concentration of the inhibitors in vivo and in vitro strongly suggest that PP1 is required for transmitting light signals. Intriguingly, several partial cDNAs encoding novel as well as conserved PP1 can be identified in maize leaves using the polymerase chain reaction. Studies of chimeric promoters indicate that PP1 activity is essential for the interaction of multiple regulatory elements. Although PP1 and PP2A have been implicated in the suppression of gene activity in yeast and animals, the present data indicate that PP1 appears to be essential for light‐dependent gene activation in plants.

Characterization of Blue Light Signal Transduction Chains That Control Development and Maintenance of Sexual Competence in Chlamydomonas reinhardtii

“…Vol. 11 5, 1997 for protein phosphatases in light-signal transduction has also been found in higher plants (Sheen, 1993).…”

Arabidopsis mesophyll protoplasts: a versatile cell system for transient gene expression analysis

“…As depicted in Figure 2c, an artificial transcription activator (ATA) is constructed with a bacterial DNA-binding domain (LexA-DB), a viral transcription activation domain (VP16) and a mammalian (rat) glucocorticoid receptor (GR). The ATA is driven under the constitutive 35S enhancer fused to the maize C4PPDK basal promoter 6 . Upon dexamethasone (DEX) treatment, the ATA (LexA-VP16-GR) is released from the cytoplasm HSP90 complex and moves into the nucleus to induce target gene transcription 26 .…”

“…1 . 6 Protoplast isolation TIMING 4-5 h 2| Choose well-expanded leaves from 3-4-week-old plants (usually true leaf numbers five to seven) before flowering (see Fig. 1a).…”

Partial Purification and Characterization of an Enzyme from Pea Nuclei with Protein Tyrosine Phosphatase Activity

“…Whereas much information is available about the structure, chemical properties, mechanism of action, and regulation of protein phosphatases in animal cells (Shenolikar and Nairn, 1991;Charbonneau and Tonks, 1992;Walton and Dixon, 1993), there is much less known about these enzymes and their functions in plant cells, despite some recent progress in this field. Severa1 Ser/Thr protein phosphatases have been reported in plant cells (Polya and Haritou, 1988;Mackintosh et al, 1991;Sheen, 1993). The activities of protein Tyr kinase and phosphatase enzymes and some phosphotyrosine protein subThis work was supported by a grant from the National Science Plant Physiol.…”