Crosstalk During Fruit Ripening and Stress Response Among Abscisic Acid, Calcium-Dependent Protein Kinase and Phenylpropanoid

Phenylpropanoids are secondary metabolites produced by plants. They, by differential expression, are involved in responses to biotic and abiotic stresses and confer plant plasticity. In addition, they are synthesized under normal conditions during the fruit-ripening process. Therefore, the understanding of the mechanics involved in the accumulation of these compounds in plants is of extreme importance for the development of plants with greater resistance and tolerance to biotic and abiotic stresses, and plants with greater functional potential. There is evidence that one of the pathways of the induction of phenylpropanoids is dependent on abscisic acid (ABA) and it is generated by a signaling cascade involving calcium (Ca2+) and Ca2+-dependent protein kinases (CDPKs). Plants have several Ca2+ binding proteins that act as cellular sensors and represent the first points of signal transduction. CDPKs are mono-molecular Ca2+-sensor/kinase-effector proteins, which perceive Ca2+ signals and translate them into protein phosphorylation and thus represent an ideal tool for signal transduction. However, the mechanisms involved in the ABA-CDPK-phenylpropanoids crosstalk under stress conditions and during fruit ripening remains uncertain. Therefore, this review seeks to surface a new line of evidence as an attempt to understand the manner in which the induction of phenylpropanoids occurs in plants.