Abstract
The physiological, biochemical and molecular mechanisms regulating the initiation of a regenerative pathway remain partially unknown. Efforts to identify the biological features that confer transformation ability, or the tendency of some cells to induce transgene silencing, would help to improve plant genetic engineering. The objective of our study was to monitor the evolution of plant cell competencies in relation to both in vitro tissue culture regeneration and the genetic transformation properties. We used a simple wheat regeneration procedure as an experimental model for studying the regenerative capacity of plant cells and their receptivity to direct gene transfer over the successive steps of the regenerative pathway. Target gene profiling studies and biochemical assays were conducted to follow some of the mechanisms triggered during the somatic-to-embryogenic transition (i.e. dedifferentiation, cell division activation, redifferentiation) and affecting the accessibility of plant cells to receive and stably express the exogenous DNA introduced by bombardment. Our results seem to indicate that the control of cell-cycle (S-phase) and host defense strategies can be crucial determinants of genetic transformation efficiency. The results from studies conducted at macro-, micro- and molecular scales are then integrated into a holistic approach that addresses the question of tissue culture and transgenesis competencies more broadly. Through this multilevel analysis we try to establish functional links between both regenerative capacity and transformation receptiveness, and thereby to provide a more global and integrated vision of both processes, at the core of defense/adaptive mechanisms and survival, between undifferentiated cell proliferation and organization.Electronic supplementary materialThe online version of this article (doi:10.1007/s11033-013-2696-y) contains supplementary material, which is available to authorized users.
Highlights
For in vitro culture-based plant transformation methods, amenability to the culture stages required for gene transfer, selection and plant regeneration is a major determinant of transformation efficiency, which is controlled by intrinsic and external factors. considerable progress has been made in the past decade, the ability to transform Triticeae species currently still lags behind that of other model plants, such as Arabidopsis thaliana or rice (Oryza sativa L.)
This paper presents the results of studies conducted at three observation levels
To the best of our knowledge there has been no report to date that establishes the molecular interconnections between tissue culture and genetic transformation competencies in plant cells
Summary
For in vitro culture-based plant transformation methods, amenability to the culture stages required for gene transfer, selection and plant regeneration is a major determinant of transformation efficiency, which is controlled by intrinsic and external factors. Considerable progress has been made in the past decade, the ability to transform Triticeae species currently still lags behind that of other model plants, such as Arabidopsis thaliana or rice (Oryza sativa L.). The delivery of DNA into cells competent for in vitro culture regeneration is one of the crucial requirements for achieving genetic engineering of plant cells. Embryogenic cultures remain the reliable and main route in regenerating transgenic cereals, regardless of the DNA transfer strategy. Considered as the most responsive explants, immature zygotic embryos (and derived calli) are the usual target tissues for wheat genetic transformation, through either microprojectile or Agrobacterium-mediated DNA delivery [5, 6]
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