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Review
. 2022 May 9:13:888425.
doi: 10.3389/fpls.2022.888425. eCollection 2022.

Molecular Determinants of in vitro Plant Regeneration: Prospects for Enhanced Manipulation of Lettuce (Lactuca sativa L.)

Tawni Bull  1   2 , Richard Michelmore  1   3
Affiliations
Review

Molecular Determinants of in vitro Plant Regeneration: Prospects for Enhanced Manipulation of Lettuce (Lactuca sativa L.)

Tawni Bull et al. Front Plant Sci. .

Abstract

In vitro plant regeneration involves dedifferentiation and molecular reprogramming of cells in order to regenerate whole organs. Plant regeneration can occur via two pathways, de novo organogenesis and somatic embryogenesis. Both pathways involve intricate molecular mechanisms and crosstalk between auxin and cytokinin signaling. Molecular determinants of both pathways have been studied in detail in model species, but little is known about the molecular mechanisms controlling de novo shoot organogenesis in lettuce. This review provides a synopsis of our current knowledge on molecular determinants of de novo organogenesis and somatic embryogenesis with an emphasis on the former as well as provides insights into applying this information for enhanced in vitro regeneration in non-model species such as lettuce (Lactuca sativa L.).

Keywords: Lactuca sativa (L.); WUSCHEL; lettuce; organogenesis; regeneration; somatic embryogenesis.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Pathways of in vitro regeneration of vascular plants. Somatic embryogenesis (SE) and de novo shoot organogenesis (DNSO) can occur directly on the explant or indirectly with the formation of pluripotent callus as an intermediate step. Species that are capable of regeneration for each pathway are represented from top to bottom: cotton, maize, Arabidopsis, and lettuce. Figure created using BioRender (https://biorender.com/).
FIGURE 2
FIGURE 2
The progression of molecular players during indirect de novo shoot organogenesis. Callus is formed on auxin rich medium and includes signaling pathways represented in box one. Shoot promersitems and meristematic centers are formed on cytokinin rich medium and include signaling pathways represented in box two. Shoot regeneration follows meristem formation and is represented by the signaling pathways included in box three. Figure created using BioRender (https://biorender.com/).
FIGURE 3
FIGURE 3
Functional domains of the shoot apical meristem (SAM). The organizing center (OC) is part of the central zone (CZ), which consists of a stem cell pool that replenishes cells to the peripheral zone (PZ) and rib zone (RB). The black arrows represent the direction of differentiating cells from the PZ to form leaf primordia (LP) and the RZ to form the stem. WUS expression is high in the OC and is regulated by CLV3/CLV1 from the CZ in a negative feedback loop. Figure created using BioRender (https://biorender.com/).
FIGURE 4
FIGURE 4
Representation of indirect de novo shoot organogenesis in lettuce. (A) A plate of 20 explants undergoing indirect de novo shoot regeneration. Black arrows represent friable callus formation at the wounded end of explants; blue arrows represent shoot regeneration from calli. (B) An explant before callus formation. (C) An explant during callus formation (black arrow). (D) First organized growth from callus (black arrow). (E) Indirect shoot regeneration (blue arrow) from callus (black arrow).
See this image and copyright information in PMC

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