In Silico Characterization and Expression Analysis of GIGANTEA Genes in Potato.

GIGANTEA (GI) genes are ubiquitous in the plant kingdom and are involved in diverse processes from flowering during stress responses to tuberization; the latter occurs in potato (Solanum tuberosum L.). GI genes have a diurnal cycle of expression; however, no details on the regulation of GI gene expression in potato have been reported thus far. The aim of our work was the analysis of the GI promoter sequence and studying GI expression in different organs and under abiotic stress conditions in potato. Two GI genes homologous to Arabidopsis GI located on chromosomes 4 and 12 (StGI.04 and StGI.12) were identified in the genome-sequenced potato S. phureja. The GI promoter regions of the commercial potato cultivar 'Désirée' were cloned and found to be almost identical to the S. phureja GI promoter sequence. More than ten TF families binding to the GI promoters were predicted. EVENING ELEMENT and ABSCISIC ACID RESPONSE ELEMENT LIKE elements related to circadian regulation and a binding site for POTATO HOMEOBOX 20 presumably involved in tuber initiation were detected in both GI promoters. However, the locations of these elements and several other cis-acting regulatory elements as well as the organ-specific expression and responses of the genes to abiotic stresses and abscisic acid were different. Thus, we presume that the function of StGI.04 and StGI.12 are at least partially different. This study lays foundation for further investigation of the roles of GI genes in potato.