TEMPRANILLO homologs in apple regulate flowering time in the woodland strawberry Fragaria vesca

Abstract

AbstractThe long juvenile period of fruit trees makes their breeding costly and time-consuming. Therefore, flowering time engineering and shortening the juvenile phase have become a breeding priority for the genetic improvement of fruit tree crops. Many economically valuable fruit trees belong to theRosaceaefamily including apples and strawberries.TEMPRANILLO(TEM) acts as a key player in flowering time control through inhibitingFTfunction. Two genes with high sequence similarity with theArabidopsis TEMgenes were isolated from apple (Malus domestica). Due to the complexity of carrying out functional studies in apple, we characterized their function in woodland strawberry as well as their expression in apple. The expression ofMdTEMgenes in apple tissues from juvenile plants was dramatically higher than that in the tissues from adult trees. In woodland strawberry, the overexpression ofMdTEMgenes down-regulatedFvFT1,FvGA3OX1, andFvGA3OX2genes in strawberry. TheMdTEM-overexpressing lines exhibited delayed flowering, in terms of days to flowering and the number of leaves at flowering. While,RNAi-mediatedsilencing ofTEMresulted in five days earlier flowering, with a lower number of leaves, a higher trichome density, and in some cases, caused in vitro flowering. According to these results and in silico analyses, it can be concluded thatMdTEM1andMdTEM2can be considered as orthologs ofFvTEMand probablyAtTEMgenes, which play an important role in regulating the juvenile phase and flowering time through regulatingFTand GA biosynthetic pathway.