Abstract
In tissue culture, the formation of callus from detached explants is a key step in plant regeneration; however, the regenerative abilities in different species are variable. While nearly all parts of organs of the dicot Arabidopsis thaliana are ready for callus formation, mature regions of organs in monocot rice (Oryza sativa) and other cereals are extremely unresponsive to tissue culture. Whether there is a common molecular mechanism beyond these different regenerative phenomena is unclear. Here we show that the Arabidopsis and rice use different regeneration‐competent cells to initiate callus, whereas the cells all adopt WUSCHEL‐RELATED HOMEOBOX 11 (WOX11) and WOX5 during cell fate transition. Different from Arabidopsis which maintains regeneration‐competent cells in mature organs, rice exhausts those cells during organ maturation, resulting in regenerative inability in mature organs. Our study not only explains this old perplexity in agricultural biotechnology, but also provides common molecular markers for tissue culture of different angiosperm species.
Highlights
We have provided cellular and molecular frameworks of callus formation in angiosperms
Regeneration-competent cells differ between the dicot Arabidopsis and the monocot rice, whereas those diverse cells adopt a common mechanism involving WUSCHEL-RELATED HOMEOBOX 11 (WOX11) and WOX5 during cell fate transition for callus initiation
Previous studies indicate that callus formation follows the rooting pathway (He et al, 2012; Liu et al, 2014; Sugimoto et al, 2010) and callus is a group of root primordium-like cells (Liu et al, 2014)
Summary
An amazing feature of plant cells is their plasticity, which endows plants with remarkable regeneration abilities (Ikeuchi, Ogawa, Iwase, & Sugimoto, 2016; Sugimoto, Gordon, & Meyerowitz, 2011; Vogel, 2005; Xu & Huang, 2014) and has been widely exploited in agricultural technologies (Sussex, 2008). Regeneration published by John Wiley & Sons Ltd. Studies of Arabidopsis thaliana suggested that the callus formation on callus-inducing medium (CIM) in tissue culture follows the rooting developmental pathway (Atta et al, 2009; Che, Lall, & Howell, 2007; He, Chen, Huang, & Xu, 2012; Liu et al, 2014; Sugimoto, Jiao, & Meyerowitz, 2010). The application of plant regeneration in tissue culture has occurred for more than half a century; a key obstacle in this biotechnology is that the ability for callus initiation upon hormone induction is highly diverse in different species. Whether there is a common molecular discipline for callus formation of different species is unclear, and how to explain the cereal problem in tissue culture is so far unanswered. We discuss the regenerative inability in mature organs of cereals
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