Signal transduction mechanisms involved in potato developmental processes

Abstract

Solanum tuberosum L. potato plants undergo several development stages during their life cycle involving stolon formation, tuberization, tuber filling, dormancy and tuber sprouting. Potato tubers are underground sinks originated from stolons in a process that requires the cessation of apex growth, the swelling of the stolon by subapical radial growth, and enlargement of the body. Potato plants produce tubers as a result of the changing balance of endogenous growth regulators, which is brought about by the plant´s ability to perceive changes in the environment. An important aspect of tuber induction is that the stimulus is received on the leaves and is graft-transmissible. Environmental and hormonal signals, such as those mediated by light and gibberellins, are integrated in the leaves and a mobile signal is exported to the underground stolons to initiate tuber formation. This process is accompanied by the accumulation of starch and storage proteins. Tuberization allows the plant to reproduce in a vegetative way and determines that it can be considered a potential perennial plant. With the onset of sprouting, the tuber turns into a source organ; the reducing sugars increase as starch is hydrolyzed, providing carbon and energy for growth of the developing sprout. Tuber development and sprouting require coordinated transcriptional and metabolic changes as well as major changes in gene expression patterns. Signalling cascades are involved in sensing and transducing the environmental and hormonal stimuli that modulate both developmental processes. In this chapter we will review the different external and endogenous factors that regulate both processes and the signal transduction cascades associated to them.