Fractal morphology: Imaging and mass spectrometry of single aerosol particles in flight

by N D Loh, C Y Hampton, M J  Bogan et al.

Nature 486 (2012)

Ultra-bright femtosecond pulses from x-ray free electron lasers (XFELs) have produced diffraction patterns of unprecedented resolution from single nanoscale objects before the onset of radiation damage.

In this work, we have developed statistical tools that probed the nanoscale heterogeneity of single soot aerosols in flight. These tools will eventually be extended to resolve high- resolution structural heterogeneity of biomolecules without the need for crystallization.

Pictured above:  Structural complexity in aerosol soot. Scale-invariant random processes drive the growth and aggregation of these aerosols, which results in fractal-like geometrical properties.

Read online: Nature.

Learn more about ND Loh’s research.

COP1 mediates the coordination of root and shoot growth by light through modulation of PIN1 and PIN2-dependent auxin transport in Arabidopsis

by Sassi, M, Lu, Y, Zhang, YH, Wang, J, Dhonukshe, P, Blilou, I Dai, MQ, Li, J, Gong, XM, Jaillais, Y, Yu, XH, Traas, J, Ruberti, I, Wang, HY, Scheres, B, Vernoux, T and Xu, Jian

Development 139, 3402-3412 (2012)

Although the roots of most plant species are not directly exposed to light, root growth is controlled by light and integrated with the growth of above-ground organs. We uncover a novel long-distance mechanism by which light signals through the master photomorphogenesis repressor COP1 to coordinate root and shoot development in Arabidopsis. We show that, in the shoot, COP1 regulates shoot-to-root transport of auxin by controlling transcription of the auxin efflux carrier gene PIN-FORMED1 (PIN1). Whereas in the root apical meristem COP1 regulates auxin transport and cell proliferation by modulating the intracellular distribution of PIN1 and PIN2 in the root, thereby ensuring rapid and precise tuning of root growth to the light environment.

Together, our results identify auxin as a long-distance signal in light-regulated plant development and show how spatially separated control mechanisms can converge on a single signalling system to coordinate development at the whole plant level.

Read online: Pubmed.

Learn more about Jian Xu’s research.

A col10a1: nlGFP transgenic line displays putative osteoblast precursors at the medaka notochordal sheath prior to mineralization

by Joerg Renn, Anita Büttner, Thuy Thanh To, Sherlynn Jin Hui Chan and Christoph Winkler

Dev Biol 2013 Sep 1;381(1):134-43

In teleosts, such as medaka, ossification of the vertebral column starts with the mineralization of the notochordal sheath in a segmental pattern. This establishes the chordal centrum, which serves as the basis for further ossifications by sclerotome derived osteoblasts generating the vertebral body.

So far, it is unclear which cells produce the notochordal sheath and how a segmental pattern of mineralization is established in teleosts. Here, we use a transgenic medaka line that expresses nlGFP under the control of the col10a1 promoter for in vivo analysis of vertebral body formation. We show that col10a1:nlGFP expression recapitulates endogenous col10a1 expression.

In the axial skeleton, col10a1:nlGFP cells appear prior to the mineralization of the notochordal sheath in a segmental pattern. These cells remain on the outer surface of the chordal centra during mineralization as well as subsequent perichordal ossification of the vertebral bodies. Using twist1a1:dsRed and osx:mCherry transgenic lines we show that a subset of col10a1:nlGFP cells is derived from sclerotomal precursors and differentiates into future osteoblasts.

For the first time, this shows a segmental occurrence of putative osteoblast precursors in the vertebral centra prior to ossification of the notochordal sheath. This opens the possibility that sclerotome derived cells in teleosts are implicated in the establishment of the mineralized vertebral column in a similar manner as previously described for tetrapods.

Read online: Pubmed.

Learn more about Christoph Winkler’s research.