Exploring the role of the two GIGANTEA genes in the life cycle length and tuberisation of the potato cultivar Désirée

Background Earliness of tuberisation is an important agronomic trait. It was demonstrated earlier that GIGANTEA (GI), a plant-specific nuclear protein that regulates multiple processes, is indirectly involved in tuberisation in a diploid potato. Commercial potatoes, including the cultivar Désirée, are tetraploids and carry two copies of GI genes, designated GI.04 and GI.12 . The aim of our study was to explore the role of the two GI genes in Désirée in relation to tuberisation. Results To obtain information on GI.04 and GI.12 functions in Désirée, mutations were introduced into the two genes individually and simultaneously using the CRISPR/Cas9 system. Two different segments of the genes were targeted by gRNAs. PCR was used for mutant identification. Three mutants from each mutagenesis were selected, and the mutations were localised at the DNA sequence level. The phenotype and tuberisation of the plants were tested by growing the plants in pots in a greenhouse. The individual mutations affecting all four copies of the genes, in general, reduced plant size. Plants of one GI.04 mutant line and two GI.12 mutant lines with truncated proteins and deletions in the 816–869 and 834–863 amino acid (a.a.) regions, respectively, were shorter and remained green for a longer time than Désirée. GI.04 and GI.12 mutants with truncation or deletion in the 567–632 a.a. and 618–694 a.a. regions, respectively, differ in phenotype; one GI.04 mutant had longer, whereas all three GI.12 mutants and the double mutants had shorter life cycles. However, only one of the GI.12 mutants and one of the double mutants tuberised earlier than Désirée. The tuber yield of the double mutant with the shortest life time was lower than that of Désirée. Conclusions Both GI genes of Désirée influence the development and life cycle length of plants. The influence of GI.12 is more pronounced than the influence of GI.04. In conjunction with the shortened lifetime, the onset of tuberisation occurs earlier.