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Title: Expression of almond KNOTTED1 homologue (PdKn1) anticipates adventitious shoot initiation

item Santos, Ana Margarida
item Oliver, Melvin - Mel
item Sanchez, Ana Maria
item Oliviera, M. Margarida

Submitted to: In Vitro Cellular and Developmental Biology - Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2011
Publication Date: 8/19/2011
Publication URL:
Citation: Santos, A., Oliver, M.J., Sanchez, A., Oliviera, M. 2011. Expression of almond KNOTTED1 homologue (PdKn1) anticipates adventitious shoot initiation. In Vitro Cellular and Developmental Biology - Plants. 48:40-49.

Interpretive Summary: In order for in vitro plant propogation methods to work efficiently it is imperative that we understand what genes control the processes of shoot formation from explant tissues such as leaf pieces or stem segments and how such genes are regulated during the propagation process. Once we know which genes regulate plant regeneration from explants we can devise superior methods for plant propagation by using the expression of such genes to mark which tissues are active in the regeneration process. Previous work had determined that a particular gene, coding for a transcription factor (a control gene) is particularly involved in the developmental switching of cells from an indeterminate growth pattern to one of determinate growth into a particular plant organ. Using gene expression studies to track the expression of this transcription factor, Knotted1, we were able to demonstrate that it is also a poweful marker for the transition of explant tissue cells into meristems that go on to form shoots. With this information we can now design propagation protocols that favor the induction of this transcription factor or use its expression to determine which cells are likely to form meristems. These results have important implications for the agricultural propagation of difficult plants, such as nut and fruit trees, that are difficult to grow from seeds or manipulate genetically. Of equal importance is the use of these findings to improve our ability to design transformation methods for species that have proven difficult to regenerate once novel genes have been inserted into their cells. This report will greatly impact the capability or agriculture to use a biotechnological approach to crop improvement.

Technical Abstract: Background and Aims: The transcription factor encoded by the gene Knotted1 is a nuclear homeodomain protein, regulating meristematic cells at the shoot apical meristem. It has been proven that Knotted1 (KN1) has a role in the switch from an indeterminate to determinate cell fate and as such this gene may potentially identify the initiation of meristem primordial development during adventitious shoot induction. Methods: An almond KN1-type gene was isolated using degenerate primers designed for the most conserved regions of the Knotted1 gene. The 5’ and 3’ ends of the isolated sequence were extended using RACE-PCR and named PdKn1 for Prunus dulcis Knotted1. RT-PCR, quantitative PCR, in situ RT-PCR and Northern blotting were used for gene expression studies. Key results: PdKn1 transcripts were detected mainly at the meristem level of different organs including stems (apical and axillary), shoot apices, and in almond and apricot leaf explants induced for adventitious meristem formation. Conclusions: The expression of PdKn1 was found to anticipate the organization of adventitious shoot meristems in almond and may reveal organogenic regions of the explants. This gene was also detected during the adventitious shoot induction of apricot, meaning that almond PdKn1 may be a useful marker for other prunoidea regeneration systems.