AGCVIII kinases: at the crossroads of cellular signaling

AGCVIII kinases regulate diverse developmental and cellular processes in plants. As putative mediators of secondary messengers, AGCVIII kinases potentially integrate developmental and environmental cues into specific cellular responses through substrate phosphorylation. Here we discuss the functionality and regulation of AGCVIII kinases. Specifically, we question the view that activities of AGCVIII kinases, like their animal counterparts, are regulated by a common regulator, 3-phosphoinositide-dependent protein kinase-1 (PDK1). Instead, increasing evidence suggests that Ca(2+) and phospholipids regulate AGCVIII kinases, by altering their activities or by affecting their subcellular localization. As AGCVIII kinases are at the crossroads of plant cellular signaling, they and the signaling networks in which they participate are keys to a better understanding of plant development and of interactions with their environment.