TEMPRANILLO Reveals the Mesophyll as Crucial for Epidermal Trichome Formation1[OPEN]

TEMPRANILLO repress epidermal trichome initiation by controlling gibberellin accumulation in the mesophyll as well as by acting as link between GA and CK signaling in the epidermis. Plant trichomes are defensive specialized epidermal cells. In all accepted models, the epidermis is the layer involved...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 2016-01, Vol.170 (3), p.1624-1639
Main Authors: Matías-Hernández, Luis, Aguilar-Jaramillo, Andrea E., Osnato, Michela, Weinstain, Roy, Shani, Eilon, Suárez-López, Paula, Pelaz, Soraya
Format: Article
Language:English
Online Access:Get full text
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Summary:TEMPRANILLO repress epidermal trichome initiation by controlling gibberellin accumulation in the mesophyll as well as by acting as link between GA and CK signaling in the epidermis. Plant trichomes are defensive specialized epidermal cells. In all accepted models, the epidermis is the layer involved in trichome formation, a process controlled by gibberellins ( GA s) in Arabidopsis rosette leaves. Indeed, GA activates a genetic cascade in the epidermis for trichome initiation. Here we report that TEMPRANILLO ( TEM ) genes negatively control trichome initiation not only from the epidermis but also from the leaf layer underneath the epidermis, the mesophyll. Plants over-expressing or reducing TEM specifically in the mesophyll, display lower or higher trichome numbers, respectively. We surprisingly found that fluorescently labeled GA 3 accumulates exclusively in the mesophyll of leaves, but not in the epidermis, and that TEM reduces its accumulation and the expression of several newly identified GA transporters. This strongly suggests that TEM plays an essential role, not only in GA biosynthesis, but also in regulating GA distribution in the mesophyll, which in turn directs epidermal trichome formation. Moreover, we show that TEM also acts as a link between GA and cytokinin signaling in the epidermis by negatively regulating downstream genes of both trichome formation pathways. Overall, these results call for a re-evaluation of the present theories of trichome formation as they reveal mesophyll essential during epidermal trichome initiation.
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.15.01309