Expression analysis of G1-1, a gene involved in tuber sprouting, by means of quantitative RT-PCR and in situ hybridisation

The process of sink to source transition in potato tuber is interrupted by a period of dormancy, in which sprout growth is completely inhibited. The transition from dormancy to sprouting is likely regulated by a large set of interacting genes. By means of Differential Display an extensive study was undertaken to identify genes differentially expressed in various stages, from dormancy to sprouting. Among different TDFs (transcriptional derived fragments) a gene called G1-1 was identified. This gene is turned off during dormancy and is activated in the early phases of tuber sprouting. Its sequence contains an intronless short open reading frame of 226 bp and did not show any homology with genes with a known function. The only similarities were found with EST clones of tomato, soybean and Arabidopsis thaliana. To get more insight about the role of G1-1 during transition from dormancy to sprouting and more extensively in the whole plant development, a detailed analysis of its expression was carried out by means of quantitative Real Time RT-PCR on different tuber tissues, sprouts and leaves. The results showed that expression of G1-1 increased in tuber buds during the first stages of sprouting, whereas almost no transcript was found in parenchyma. The highest level of expression was found in sprouts and in developing leaves. Experiments of in situ hybridisation showed that G1-1 transcript was localised mainly in shoot apical meristem, suggesting that the expression of this gene is highly correlated to meristematic activity of potato tissues.