chloroplast

Scientists solve plant sperm puzzle

Chloroplasts are where plant cells perform photosynthesis and wheat, like many other plants, inherits chloroplasts only from the mother through small precursors called plastids.  

But how this happened was unknown – why didn’t the male’s chloroplast DNA travel with the rest in sperm? 

By tagging plastids in wheat with a protein that glowed green scientists at Rothamsted Research and the University of Manchester could watch them in developing pollen grains. They saw for the first time that plastids are degraded in sperm cells just before fertilisation, meaning only plastids from the mother plant are inherited by the offspring.

In the image above the top line shows the protein attached to the plastids in wheat pollen, in the bottom row it is untargeted.

The finding could be used to help breed better strains of wheat, one of the world’s most important and valuable crops.

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Image: Huw Jones, Rothamsted Research

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ATP synthesis. The chemiosmotic hypothesis by Peter Mitchell had four postulates. Here, we explore them all.

Electrons lose some redox potential as they are transported through an ETC. Some of that energy can be reclaimed in establishing an electrochemical gradient. The Q cycle is one way - see my sheet on this for a fuller explanation - and conformational changes in proton pumps like in Complex I is another, although this is less well understood.

The membrane is fairly impermeable to protons. Using an proton ionophore uncouples the proton gradient from ATP synthesis. These act as uniports of protons back into the matrix/stroma. The example used here is 2,4-dinitrophenol (DNP), which is attracted to the positive face of the membrane when unprotonated and to the less negative face when protonated.

The proton gradient drives ATP synthase. Protons return to the matrix/stroma via c subunits in the F0 subunit of ATP synthase. This turns the γδε rotor relative to three dimeric αβ subunits, which are held still by a stator, in the F1 subunit. Rotation causes conformational changes in the αβ subunits, which cycles them through loose, tight, and open conformations, which makes ATP. ATP synthase working in reverse is an ATPase, and mammalian IF1 protein jams this function.

And finally, translocators feed ADP and Pi into the system.

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ATP synthesis by Ayraethazide is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

ONE-CELLED PLANKTONIC ORGANISM HAVE ANIMAL-LIKE EYES

Multicellularity is often considered a prerequisite for morphological complexity, as seen in the camera-type eyes found in several groups of animals. A notable exception exists in single-celled eukaryotes called dinoflagellates, some of which have an eye-like ‘ocelloid’ consisting of subcellular analogues to a cornea, lens, iris, and retina

According to a canadian research team at the University of British Columbia, the single celled organism called  warnowiid dinoflagellate evolved a tiny version of a multi-cellular eye. In fact, contains a collection of sub-cellular organelles that look very much like the lens, cornea, iris and retina of multicellular eyes found in large animals.  The ocelloid, who is named the structure, could be used to detect shifts in light as it passed through their transparent prey

This process is known as convergent evolution, when different animals can evolve similar traits in response to their environments.

Warnowiids are found in marine plankton, little is known about their life histories, because they cannot be cultured in the laboratory, and samples obtained from the natural environment do not survive well under laboratory conditions

Light micrograph of a single Warnowia isolate. Scale bar = 10 microns, from Hoppenrath et al. 2009. 

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cytoplasm streaming (movement of cytosol) carrying chloroplasts around the edges of the plant cells.