Anisocotyly and meristem initiation in an unorthodox plant, <Emphasis Type="Italic">Streptocarpus rexii</Emphasis> (Gesneriaceae) |
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Authors: | Raffaella Mantegazza Michael Möller C Jill Harrison Simone Fior Chiara De Luca Alberto Spada |
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Institution: | (1) Dipartimento di Biologia, Universita degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy;(2) Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh, EH3 5LR, Scotland, UK;(3) Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK;(4) CNR, Istituto di Biofisica, Sede Milano, Italy |
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Abstract: | In common with most Old World Gesneriaceae; Streptocarpus Lindl. shows anisocotylous growth, i.e., the continuous growth of one cotyledon after germination. Linked to this phenomenon
is an unorthodox behaviour of the shoot apical meristem (SAM) that determines the growth pattern of acaulescent species (subgenus
Streptocarpus). In contrast caulescent species develop a conventional central post-embryonic SAM (mainly subgenus Streptocarpella). We used S. rexii Lindl. as a model to investigate anisocotyly and meristem initiation in Streptocarpus by using histological techniques and analyses of the expression pattern of the meristematic marker SrSTM1 during ontogeny. In contrast to Arabidopsis thaliana (L.) Heynh., S. rexii does not establish a SAM during embryogenesis, and the first evidence of a SAM-like structure occurs during post-embryonic
development on the axis (the petiolode) between the two cotyledons. The expression pattern of SrSTM1 suggests a function in maintaining cell division activity in the cotyledons before becoming localized in the basal meristem,
initially at the proximal ends of both cotyledons, later at the base of the continuously growing macrocotyledon, and the groove
meristem on the petiolode. The latter is equivalent to a displaced SAM seemingly originating de novo under the influence of
endogenous factors. Applied cytokinin retains SrSTM1expression in the small cotyledon, thus promoting isocotyly and re-establishment of a central post-embryonic SAM. Hormone-dependent
delocalization of the process of meristem development could underlie anisocotyly and the unorthodox SAM formation in Streptocarpus.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. |
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Keywords: | Anisocotyly Cytokinins Groove meristem Shoot apical meristem SrSTM1 Streptocarpus |
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