The Tomato BLADE ON PETIOLE and TERMINATING FLOWER Regulate Leaf Axil Patterning Along the Proximal-Distal Axes.

Anat Izhaki,Yuval Cinnamon,John P Alvarez,Yoram Eyal,Raya Liberman-Aloni,Olga Genin

doi:10.3389/fpls.2018.01126

Anat Izhaki, Yuval Cinnamon + Show 4 more

Open Access

https://doi.org/10.3389/fpls.2018.01126

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Abstract

Leaf axil patterning occurs concomitantly with leaf development and takes place at the boundary zone which demarcates the initiating leaf primordium from the shoot apical meristem. Subsequent growth and differentiation result in establishment of the axillary meristem and abscission zone (AZ) along the proximal-distal axis of the leaf axil, yet the molecular mechanisms that regulate these events are poorly understood. We studied the role of the tomato BLADE ON PETIOLE (SlBOP) boundary gene family on the development of the leaf axil using BOP-silenced plants as well as BOP-mutated lines. We show that silencing of the tomato SlBOP gene family affects patterning of the leaf axil along the proximal-distal axis, manifested by dispositioning of the AM and abnormal development of the adjacent tissue resulting in lack of a functional leaf AZ. Dissection of the role of each of the three tomato SlBOPs by analysis of single, double and triple null-mutants demonstrated that SlBOP2 is the dominant gene in leaf axil patterning, but does not rule out involvement of SlBOP1 and SlBOP3 in correct AM positioning. We further studied the potential role of TERMINATING FLOWER (TMF), a transcription factor which was previously shown to interact with SlBOPs, in leaf axil patterning using TMF mutant tomato lines. The results suggest that similar to SlBOP2, TMF is involved in leaf axil proximal-distal patterning and AZ development.

Highlights

The shoot apical meristem (SAM) is established during embryogenesis and serves as the origin of plant vegetative development and the indeterminate pattern of plant growth
In tomato SlBOP genes are expressed in leaf primordium boundary zone (BZ) during early stages of leaf primordium development (Xu et al, 2016), yet, very little is known regarding their function in later stages of leaf axil patterning and axillary meristems (AMs) development
Leaf axil patterning along the proximal-distal axis begins as the leaf primordium emerges from the peripheral zone of the SAM and a new BZ is established between the SAM and the developing leaf primordium

Summary

Introduction

The shoot apical meristem (SAM) is established during embryogenesis and serves as the origin of plant vegetative development and the indeterminate pattern of plant growth. Vegetative growth and development occurs in the SAM by a fine balance between two types of cells – meristematic cells which maintain a non-differentiated identity, and cells which depart from the meristem and differentiate to produce organ primordia (Bowman and Eshed, 2000; Barton, 2010). Differentiation of the AM takes place in BZs early in development, concomitantly with leaf initiation, and requires auxin minima achieved by polar auxin transport from the primordium toward the SAM (Wang Q. et al, 2014; Wang Y. et al, 2014; Burian et al, 2016; Wang et al, 2016)

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