Abstract
The causal relationship between cell division and growth in plants is complex. Although altered expression of cell-cycle genes frequently leads to altered organ growth, there are many examples where manipulation of the division machinery leads to a limited outcome at the level of organ form, despite changes in constituent cell size. One possibility, which has been under-explored, is that altered division patterns resulting from manipulation of cell-cycle gene expression alter the physiology of the organ, and that this has an effect on growth. We performed a series of experiments on retinoblastoma-related protein (RBR), a well characterized regulator of the cell cycle, to investigate the outcome of altered cell division on leaf physiology. Our approach involved combination of high-resolution microCT imaging and physiological analysis with a transient gene induction system, providing a powerful approach for the study of developmental physiology. Our investigation identifies a new role for RBR in mesophyll differentiation that affects tissue porosity and the distribution of air space within the leaf. The data demonstrate the importance of RBR in early leaf development and the extent to which physiology adapts to modified cellular architecture resulting from altered cell-cycle gene expression.
Highlights
Research over the last two decades has provided fundamental insight into the plant cell cycle, identifying the lead genes involved in progression through the cycle and providing a significant understanding of their regulation by both endogenous developmental programmes and external triggers (De Veylder et al, 2007)
We describe here a series of experiments in which we have used combined micro X–ray computed tomography (microCT) imaging and fluorescence/gas exchange analysis to investigate the physiological outcome of suppression of a key cell-cycle regulator, retinoblastoma-related protein (RBR)
MicroCT allows 3D imaging of objects in an essentially non-invasive fashion (Kaminuma et al, 2008; Dhondt et al, 2010; Tracy et al, 2010), and recent advances in this technology have led to a significant improvement in both the resolution and speed of data capture, extending its potential applications for plant sciences (Pajor et al, 2013). This approach enabled a quantitative analysis of the morphological and histological outcome of altered RBR expression that may be related to leaf physiology, and, allowed us to characterize an unanticipated facet of RBR function in leaves – the control of mesophyll differentiation
Summary
Research over the last two decades has provided fundamental insight into the plant cell cycle, identifying the lead genes involved in progression through the cycle and providing a significant understanding of their regulation by both endogenous developmental programmes and external triggers (De Veylder et al, 2007). One possibility, which has been little considered, is that the altered division pattern and size resulting from manipulating cell-cycle genes has a significant effect on leaf physiology, and it is this flexibility in the linkage of cell division pattern, physiology and growth that accounts for. We describe here a series of experiments in which we have used combined microCT imaging and fluorescence/gas exchange analysis to investigate the physiological outcome of suppression of a key cell-cycle regulator, retinoblastoma-related protein (RBR)
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