The grapevine's gene expression analysis reveals two distinct molecular and functional phases that correspond with the green and red grape stages. And researchers have reported the first biochemical evidence that reactive oxygen species accumulate during the colour transition. Stefania Pilati and fellow researchers from the IASMA Research Center, San Michele all'Adige, Italy, investigated ripening Pinot Noir grapes (Vitis vinifera L.) to identify fruit ripening genes and investigate seasonal influences. They found a core set of more than 1,400 ripening-specific genes that fluctuated similarly across three growing seasons and a smaller gene group strongly influenced by climatic conditions.
During the green berry (pre-véraison) phase, numerous genes involved in hormonal signalling and transcriptional regulation were modulated, suggesting large-scale cellular metabolism reprogramming. Auxin, ethylene and light played pivotal roles. During the following ripening (post-véraison) phase, genes for cell-wall organization and biogenesis, carbohydrate and secondary metabolisms, and stress response came into play, whereas photosynthesis was strongly repressed. These transcriptional events tally with the processes of berry softening and accumulation of sugar, colour and aroma compounds, which ultimately determine berry and wine quality. At véraison, the intervening point when grapes slow down their growth and change colour, this study highlighted an oxidative burst involving hydrogen peroxide (H2O2), and an extensive modulation of the enzymatic anti-oxidative network.
Meanwhile, Laurent G. Deluc and colleagues from the University of Nevada, Reno and the Boston University School of Medicine, USA, took a closer look at the V. vinifera Cabernet Sauvignon variety, surveying seven different stages of grape berry development. The team mapped pronounced differences throughout development in messenger-RNA (mRNA) expression for genes that play key functional roles in a host of processes. These included organic and amino acid metabolism, photosynthesis, circadian cycles and pathogen resistance.
In particular, the researchers recorded changes associated with transcription factor expression patterns, abscisic acid (ABA) biosynthesis, and calcium signalling genes that identified candidate factors likely to participate in véraison, or aroma compound production, and in pathway regulation and sequestration of flavonoid compounds. Some mRNAs were observed to decrease or increase specifically throughout ripening and sugar metabolism gene expression pattern analysis revealed an alternative and previously uncharacterised pathway for glucose and triose phosphate production invoked from véraison to mature berries.
Despite the grapevine's importance, genetic cues underlying the biochemical and physical changes during berry and flavour development have lain undiscovered - until now. "The large number of regulatory genes we have identified represents a powerful new resource for dissecting the mechanisms of fruit ripening control in non-climacteric plants", Pilati and co-workers say. Meanwhile, the second team say they have identified "a set of previously unknown genes potentially involved in critical steps associated with fruit development that can now be subjected to functional testing".
Charlotte Webber | alfa
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The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
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Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
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For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
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