Antisense Expression of MdTFL1, a TFL1-like Gene, Reduces the Juvenile Phase in Apple

Abstract

<jats:p>Because fruit trees such as apple (<jats:italic>Malus</jats:italic> ×<jats:italic>domestica</jats:italic> Borkh.) flower and set fruit only after an extended juvenile phase lasting several years, efficient breeding of fruit trees is limited. We previously suggested that <jats:italic>MdTFL1</jats:italic> (<jats:italic>Malus</jats:italic> ×<jats:italic>domestica TFL1</jats:italic>) functions analogously to <jats:italic>TERMINAL FLOWER 1</jats:italic> (<jats:italic>TFL1</jats:italic>) and that <jats:italic>MdTFL1</jats:italic> is involved in the maintenance of the juvenile/vegetative phase in apple. To clarify the function of <jats:italic>MdTFL1</jats:italic> in apple, we produced transgenic `Orin' apple trees expressing <jats:italic>MdTFL1</jats:italic> antisense RNA. One of them flowered only 8 months after the transfer to the greenhouse, whereas the nontransformed control plants have not flowered in nearly 6 years. As expected, the expression of endogenous <jats:italic>MdTFL1</jats:italic> was suppressed in the transgenic lines that showed precocious flowering. In addition, the expression level of the transgene was correlated with the reduction of the juvenile phase. These findings confirm that <jats:italic>MdTFL1</jats:italic> functions like <jats:italic>TFL1</jats:italic> and that <jats:italic>MdTFL1</jats:italic> maintains the juvenile and vegetative phase in apple. Flower organs of the transgenic apple trees were normal in appearance, and a precocious flowering transgenic line set fruit and seeds. Interestingly, some flowers of the transgenic apple trees developed without undergoing dormancy. The expression of <jats:italic>MdTFL1</jats:italic> in apple may affect flower development as well as flower induction.</jats:p>

Development of a transgenic early flowering pear (Pyrus communis L.) genotype by RNAi silencing of PcTFL1-1 and PcTFL1-2

“…The eVects of several major Xowering-regulator genes, among them FT, AP1, LFY, FUL and TFL1, on juvenility have been studied in diVerent tree species including apple (for example, see Endo et al 2005;Kotoda et al 2006Kotoda et al , 2010Szankowski et al 2009;Matsuda et al 2009;Flachowsky et al 2007;Tränkner et al 2010). Our aim was to develop a transgenic pear with a short juvenile phase that could pass on the trait to subsequent generations.…”

“…In the transgenic pear line EF-Spa, solitary Xower developed rapidly, taking only 2 weeks to complete with no need for chilling. Similarly, down regulation of the TFL-1 gene and over-expression of the FT gene in apple, resulted with juvenile free stunted plants (Kotoda et al 2006(Kotoda et al , 2010Tränkner et al 2010). Over-expression of the BpMADS4 gene in apple induced rapid development of solitary Xowers with no need for chilling ).…”

“…Gene transformation has been used to shorten the juvenile period in several tree species (for example see, Pena et al 2001;Hsu et al 2006;Kotoda et al 2006;Hanke et al 2007;Flachowsky et al 2007Flachowsky et al , 2009. In apple, antisense expression of MdTFL1 shortened the juvenile period from 5 years in non-transgenic trees to several months (Kotoda et al 2006).…”

“…In apple, antisense expression of MdTFL1 shortened the juvenile period from 5 years in non-transgenic trees to several months (Kotoda et al 2006). Overexpression of the FRUITFUL (FUL) homologue from silver birch (Betula pendula Roth.)…”

Over-expression of an FT-homologous gene of apple induces early flowering in annual and perennial plants

“…Over-expression of the gene BpMADS4 from Betula pendula in apple shortened the juvenility and induced Xowering during in vitro cultivation . Transgenic apple trees with antisense expression of the apple TERMINAL FLOWER 1 (MdTFL1) gene Xowered 8 months after transfer to the greenhouse (Kotoda et al 2003(Kotoda et al , 2006, whereas overexpression of the Arabidopsis Xoral promoter gene LEAFY (LFY) led to a columnar phenotype with shorter internodes but did not accelerate Xowering (Flachowsky et al 2010).…”