Role of Ca 2+-mediated signaling in potato tuberization: an overview

Abstract

Potato tuberization represents the morphogenetic transition of underground shoot to tuber involving several biochemical and molecular changes under complex environmental, nutritional and endogenous regulation. Among the nutritional factors, the role of calcium in potato tuberization is documented in several earlier studies. Calcium is a major essential nutrient required for normal growth and development of plants. As a second messenger it plays a role in a number of fundamental cellular processes like cytoplasmic streaming, thigmotropism, gravitropism, cell division, cell differentiation, photomorphogenesis, plant defense and various stress responses. Calcium in the cytosol regulates the activity of Ca 2+-sensor proteins and these proteins will subsequently activate and/or modify the activity of target proteins in biological pathways. Also, cytosolic calcium regulates oxidative burst via calcium dependent protein kinases (CDPKs) and induces many intracellular signaling pathways. Studies suggest that Ca 2+ and Ca 2+-sensor protein calmodulin (CaM) have a role as signal molecules for tuber induction in potato. Also, a potato Ca 2+-dependent protein kinase, StCDPK1, is reported to be transiently expressed in tuberizing stolons suggesting its possible involvement in potato tuberization by transcriptional activation of some of the tuberizing genes. Though Ca 2+ and Ca 2+-regulated proteins influence many developmental processes in plants, the exact molecular and biochemical mechanism of Ca 2+-mediated signal pathways controlling potato tuberization is still not clear. This review sheds some light on the possible molecular mechanisms involved in the Ca 2+-mediated signaling in potato tuberization.