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Heat mediated silencing of MdTFL1 genes in apple (Malus × domestica)

Weigl, Kathleen, Flachowsky, Henryk, Peil, Andreas, Hanke, Magda-Viola
Plant cell, tissue, and organ culture 2015 v.123 no.3 pp. 511-521
Malus, apples, cultivars, flowering, gene expression regulation, greenhouses, heat, leaves, shoots, transgenes, transgenic plants
The apple TFL1 genes, MdTFL1-1 and MdTFL1-2, were tried to be silenced using the opposing dual-promoter gene construct 620p9U10-HSP::MdTFL1-HSP containing a 323 bp fragment of MdTFL1-1 flanked by two inverted sequences of the Gmhsp17.5-E heat-inducible promoter. This construct was used for transformation experiments with the apple cultivars ‘Gala’ and ‘Pinova’. Three (T967, T973, and T985) and two (T976 and T987) transgenic lines were obtained for ‘Pinova’ and ‘Gala’, respectively. Single heat shock treatments at 42 °C for 1 and 2 h, respectively, were applied to plants of transgenic lines and non-transformed controls grown in vitro or in the glasshouse. Heat shock treatments induced a short-term activation of the transgene construct. Silencing of MdTFL1-1 and MdTFL1-2 was detected in transgenic plants, but also in non-transformed controls, highlighting a similar heat response. The transcription of both MdTFL1 genes was repressed for 24 h post heat shock induction. In parallel, we treated shoots of glasshouse-grown plants at 42 °C for 2 h daily for the duration of 28 days. This treatment resulted in silencing of MdTFL1 in leaves of transgenic and non-transformed plants. However, repeated heat shock treatments failed to induce flower development in plants. Notwithstanding, we recorded a number of deformed leaves on transgenic shoots in comparison to non-transformed ones. This has lead to the conclusion that the transgene construct is functional in down-regulation of TFL1 homologs. The heat shock treatments demonstrated a major role of both MdTFL1 genes in plant’s heat response.