Gene expression profiling of leaves in conjunction with a floral bud differentiation process in cultivated strawberry 'Akihime'

In Japan, a forcing culture treatment is commonly used for harvesting June-bearing strawberry cultivars from November to next May. It is necessary to transplant daughter plants at the early stage of floral development in this system, and a microscopic observation of the crown tissue is the only one technique for judging the floral differentiation stage. However, as the microscopic observation needs dedicated trained staffs, development of a novel simple technique is strongly demanded. In this study, we attempted to identify genes of which the expression in leaf is changed synchronously with a transition from the shoot apical meristem to floral meristem as candidates for biomarkers. June-bearing cultivar `Akihime' plants were treated with a flowering-inductive intermittent low temperature storage treatment or non-floweringinductive (long day and high temperature) condition and the floral differentiation stage of them were determined by the microscopic observation and quantitative PCR of floral regulators FaFT3 and FaTFL1-1 in laser-microdissected meristem cells. Then, total RNAs of leaf were extracted from plants at undifferentiated (stage 0), very early floral meristem differentiation (stage A), or early meristem differentiation (stage B) with three biological replicates each and used for RNA-seq analysis. Clustering and differentially expressed genes analysis revealed that the expression profiles differed significantly between the vegetative ( i.e., stage 0) and reproductive (i.e., stage A or stage B) even in leaves. We further identified nine genes that are rarely expressed in leaves of strawberry plants at the vegetative phase, but are highly expressed in leaves of strawberry plants at the reproductive phase, which are potential biomarker candidates.