Ferreira et al. BMC Genomics 2010, 11:93 http://www.biomedcentral.com/1471-2164/11/93 Page 6 of 17 Figure 3 Diurnal expression of genes known to be involved in starch biosynthesis. A) Import of glucose 6-phosphate and ATP into the plastid and the conversion thereof to ADP-Glucose. GPT1 (light blue), GPT2 (dark blue), PGM (orange), NTT1 (brown), AGPase LS (light green), AGPase SS (dark green). B) Starch synthases and branching enzymes. SSII (dark grey), SSIII (light grey), GBSS (blue), SSIV (black), SBEA (light purple), SBEB (dark purple), ISA1 (dark red) and ISA2 (pink). C) Photosynthetic and Calvin cycle related genes. Plastocyanin (pink solid), CAB ( pink dotted), Rubisco (blue dotted), TPT (blue solid). D) Sucrose cleavage and phosphorylation. CW-Inv (olive green), FK (blue), Susy (gold), HK1 (dark yellow) and HK2 (green) Values are the mean of two replicates. starch degradation in Arabidopsis and other organisms proceeds via ί-amylase [32]. Starch must first be phos- phorylated by glucan-water dikinase (GWD), and to a lesser extent phospho-glucan water dikinase [33,34]. It is then either directly degraded to maltose by ί-amylase or first to linear glucans by Isoamylase 3. Before complete hydrolysis of phosphorylated glucans can occur, phos- phate groups must be removed by specific a phosphatase, known as SEX4 phosphoglucan phospha- tase [35]. The linear glucans are then hydrolysed to mal- tose by ί-amylase. Maltose is subsequently exported to the cytosol via the maltose transporter (MEX1) [36] and it is believed that the disproportioning enzyme 2 (DPE2) plays an important role in its further degradation [37]. Maltose can also be degraded by disproportioning enzyme 1 (DPE1) inside the plastid. For potato evidence Figure 4 Relative expression of GPT and NTT in epidermal and whole leaf tissue. A) GPT and B) NTT. Error bars represent standard deviation (n = 3).