Because they're not red(!)
Although this may appear to be a flippant answer to the question ‘Why are plants green?’, it's probably not too wide of the mark. Many interested parties have wrestled with the question and several suggestions have been made as to why most plants – by which they tend to mean the principal photosynthetic parts, the leaves – are predominantly green in colour. Most of these dwell on the preponderance of green-coloured chlorophylls (yes, a and b; http://en.wikipedia.org/wiki/Chlorophyll) in land plants. See MinuteEarth's charming video about this at http://bit.ly/10l9nwr, or ResearchGate's academically contributed thread on this issue at http://www.researchgate.net/post/Why_are_plants_green, or the undergraduate-student-targeted item by Mark McGinley (an Associate Professor in the Honors College and Department of Biological Sciences at Texas Tech University in Lubbock, USA) at http://bit.ly/10la0Gt. However, it seems that the ‘real’ answer relates to the evolutionary heritage of the land flora, as deduced by Jonas Collén et al. and their announcement of the sequencing of the genome of Chondrus crispus (PNAS 110: 5247–5252, 2013), a red alga/seaweed commonly called Irish moss. Although red algae contain green chlorophyll, their red coloration is a result of large amounts of non-green pigments such as phycoerythrin (http://www.ucmp.berkeley.edu/protista/rhodophyta.html). During the inferred course of its evolution, C. crispus lost many genes (its compact genome of 9606 genes compares with the unicellular green alga Chlamydomonas reinhardtii with 14 516 genes, and Arabidopsis thaliana's 27 416). This genetic reductionism would have had evolutionary knock-on effects. In particular, the loss of flagellar genes, needed for the motility of certain cells – especially the gametes during sexual reproduction in so-called ‘lower’ land plants (http://bit.ly/140WrKD) – may have been enough to have given ‘rival’ flagellate green algae the evolutionary ‘leg-up’ needed to allow them to claim the land as their own, and ultimately to beget the land flora (http://en.wikipedia.org/wiki/Evolutionary_history_of_plants): ‘Had this massive gene loss never occurred, red algae might have extensively colonized the terrestrial environment, in the same way as green algae, which are the ancestors of all land plants’ (http://bit.ly/16Sqet6). And that's why plants are green/aren't red. ‘Just so!’, an exceedingly well-informed Mr Kipling is reported to have said (http://en.wikipedia.org/wiki/Just_So_Stories).
Image: Franz Eugen Köhler, Köhler's Medizinal-Pflanzen. Gera-Untermhaus, 1897.
Prizes for plant scientists …
Why are botanical FRSs like buses? You wait for ages for one to come along, and then three appear at once! On a more serious note, great news that two of the staff at the UK's Norwich-sited John Innes Centre (JIC, ‘an independent, international centre of excellence in plant science and microbiology’ whose ‘mission is to generate knowledge of plants and microbes through innovative research, to train scientists for the future, to apply our knowledge to benefit agriculture, the environment, human health and well-being …’) have just received this great honour (http://news.jic.ac.uk/2013/05/royal-society-jic-fellows/). Professor Mike Bevan (JIC Deputy Director) was elected to Fellowship of the UK's Royal Society (one of the poshest science clubs in the world; http://en.wikipedia.org/wiki/Royal_Society) for his work that has pioneered methods for expressing foreign genes in plants that underpin the crop biotechnology industry. He has also recently helped to complete the first draft of the wheat genome (Nature 491: 705–710, 2012), which should accelerate breeding and genetic analysis of this globally important crop. Professor Melvin Bibb's focus is on how soil (plants grow in soil and interact with microbes so I'm claiming him as ‘one of our own’, however tenuous the association!) bacteria such as Streptomyces make antibiotics and his breakthroughs assist drug companies in their quest to make new and improved antibiotics. And also elected to Fellowhip in 2013 (http://royalsociety.org/about-us/fellowship/new-fellows-2013/) is Professor Stephen Long (Edward William and Jane Marr Gutgsell Endowed Professor of Plant Biology and of Crop Sciences at the University of Illinois, USA; http://royalsociety.org/people/stephen-long/), whose plant credentials are listed thus, ‘Stephen Long is a pre-eminent plant environmental physiologist distinguished by his pioneering work on photosynthetic responses to global atmospheric change and the demonstration that C4 plants can achieve high productivity in temperate climates’. I hope they will all be pleased to know that they now rank aside such notables as Sir Isaac Newton, Charles Darwin, Richard Dawkins, Ottoline Leyser and Prince Andrew (elevated to Royal Fellowship in 2013; http://royalsociety.org/people/andrew-york/). Intriguingly, there is already a Professor Michael Bevan FRS, but who is Professor of Immunology at the University of Washington, USA. You don't believe me? Well – and in keeping with the society's motto Nullius in verba (Latin for ‘Take nobody's word for it’; http://royalsociety.org/about-us/history/) – check it out at http://royalsociety.org/about-us/fellowship/fellows/ and at http://immunology.washington.edu/michael-j-bevan-phd-frs. Still, I do wonder what would happen if both Michael Bevan FRSs occupied the same place at the same time …
[For interesting commentary on the number of women amongst the newly elected – and existing – FRSs, see Cambridge University's Professor Athene Donald's article at http://bit.ly/10hPIrF. For disquiet regarding HRH the Duke of York KG GCVO (kpa* Prince Andrew)'s fellowship, see the news item by James Wilsdon (Professor of Science and Democracy at the University of Sussex and previously director of science policy at the Royal Society) at http://bit.ly/12cOJwW – Ed. *kpa = ‘known politely as …’]
Image: Tom Morris/Wikimedia Commons.
… Prizes for plant sites
There has been considerable interest in the attempt by the Singapore Botanic Gardens to attain recognition as a UNESCO (United Nations Educational, Scientific and Cultural Organization; http://bit.ly/12axlcp) World Heritage Site (http://whc.unesco.org/en/about/). Since late in 2012 the site has had ‘Tentative’ status – a step toward full recognition (http://whc.unesco.org/en/tentativelists/5786/) – but now wants to go the whole way. Founded in 1859 while the island was under British colonial rule, the gardens are a ‘lush and serene 74-hectare (182-acre) park on the edge of downtown Singapore’ and ‘boast over 30,000 plant and tree species’ (http://bit.ly/10lkg1n). If its bid is accepted it would join existing Heritage Site botanical gardens in Padua (Italy; http://en.wikipedia.org/wiki/Orto_botanico_di_Padova) and the Royal Botanic Gardens at Kew (England; http://whc.unesco.org/en/list/1084). Heritage Status is not guaranteed, but with Chris Blandford Associates involved (who helped to get Kew listed as a World Heritage Site in 2003; http://bit.ly/12axXPe) hopes must be high. And botanic gardens are not just pleasant places for a stroll; these sites have important survival value for all of us. As repositories of living specimens and plant knowledge their role embraces maintenance of ‘documented collections of living plants for the purposes of scientific research, conservation, display, and education’ (https://en.wikipedia.org/wiki/Botanical_garden). But they go far beyond that, as pointed out by Arthur Hill in his review of the history and functions of botanic gardens (Annals of the Missouri Botanical Garden 2: 185–240, 1915). Indeed, given current – and continued future – concerns about food crops, plants' ability to cope with climate change, etc, as Peter Crane et al. remind us, ‘at no other point in history has research in botanic gardens and arboreta, been more important’ (Trends in Plant Science 14: 575–577, 2009). We should therefore not only be honouring the globe's more high-profile botanic gardens, but also be actively promoting the important role played by, and research carried out in, all botanic gardens worldwide. This is a goal embraced by BGCI (Botanic Gardens Conservation International; http://www.bgci.org/global/mission/), and important to the Global Strategy for Plant Conservation (GSPC; Stephen Blackmore et al., Botanical Journal of the Linnean Society 166: 267–281, 2011). But that's not to say that we shouldn't look after our national gardens and spend nearly £15 million giving Kew's iconic Temperate House a ‘make-over’ (http://bit.ly/18SCEOs).
Image: Wikimedia Commons.
Algae found under teenager's bed …
Shock, horror! But no surprises there you might think. After all, teenagers' bedrooms are notorious ‘no-go’ areas for their parents – and others of a sensitive nature – and anything can develop (even new life forms!) in the insalubrious environment contained therein. But this is no ordinary tale of teenage grot. Rather, it is a carefully planned experiment carried out by 17-year old Sara Volz who was trying ‘to use guided evolution, so artificial selection, to isolate populations of algae cells with abnormally high oil content’, (http://nbcnews.to/10mz2jQ). Entitled ‘Optimizing algae biofuels: artificial selection to improve lipid synthesis’, her investigation used the herbicide sethoxydim to kill algae with low levels of acetyl-CoA carboxylase (ACCase), an enzyme crucial to lipid synthesis (http://bit.ly/YCLTD7). Under this strong environmental pressure, the remaining artificially selected algae cells revealed significant increases in lipid accumulation. If those cells can be sustained, artificial selection could be used to increase microalgal oil yields and make algae biofuel viable. Well, her inquisitiveness within an imaginative laboratory setting(!) earned Sara (representing Cheyenne Mountain High School, Colorado Springs, USA) top prize in the Intel Science Talent Search (Intel STS), ‘the nation's [i.e. USA's] most prestigious science research competition for high school seniors’ (http://www.societyforscience.org/sts). The US$100 000 scholarship should go a long way to funding her studies at Massachusetts Institute of Technology (USA) where she is destined this autumn. As will what remains of the US$50 000 Davidsons Fellowship Scholarship Sara won in 2012 for a project entitled, ‘Enhancing algae biofuels: investigation of the environmental and enzymatic factors effecting algal lipid synthesis’ (http://bit.ly/1414HdA). More usually employed as a post-emergence herbicide to control grass weeds in broad-leaved crops, sethoxydim apparently also has ‘indoor uses’ http://bit.ly/10lqJt6). However, one imagines that the good people at Cornell didn't envisage such an indoor use!
[Now, I don't want to be picky, but to subject these claims to proper scrutiny, etc, we do need to know what the algae were. So, I did my own research, and eventually managed to find that Sara has ‘worked with several different strains – the ones I use currently are Chlorella vulgaris and Nannochloropsis salina …’ (http://bit.ly/13fdaLo). But that information seems to predate the 2013 Intel STS project. So, we're still uncertain of the species. Nevertheless, this young scientist is definitely one to watch! And not just because she was listed as one of the top 10 teen inventors in the USA by Popular Science magazine as far back as September 2011 (http://bit.ly/17JJYgG) – Ed.].
Image: Wikimedia Commons.
Focus on transfer cells
I love transfer cells. They are plant cells (which is great), but with a difference; they are ‘specialized parenchyma cells that have an increased surface area, due to infoldings of the plasma membrane. They facilitate the transport of sugars from a sugar source, mainly leaves, to a sugar sink, often developing fruits. They are found in nectaries of flowers and some carnivorous plants’ (http://en.wikipedia.org/wiki/Transfer_cell). Those plasma membrane infoldings are the result of cell wall ingrowths and transfer cells (TCs) appear to have been present in angiosperms for over 50 million years (Marc Gottschling and Hartmut Hilger, American Journal of Botany 90: 957–959, 2003). The term ‘transfer cell’ was coined in recognition of proposed general functions in transferring solutes between interconnected protoplasts (symplast) and non-living spaces (apoplast) in or surrounding the plant (Brian Gunning, Current Contents 43: 18, 1983). TCs are found in many widely dispersed plant types and their importance probably lies in their role in nutrient distribution, as they facilitate high rates of transport at sites that might otherwise present ‘bottlenecks’ for apo-/symplasmic solute exchange; e.g. crop yield in many species may ultimately depend as much upon proper functioning of internal TCs as it does on externally applied fertiliser(!). So, the more that is known about development, etc, of TCs the better for all of us. Well, good news then that Kiruba Chinnappa et al. have developed phloem parenchyma TCs in Arabidopsis as an experimental system to identify transcriptional regulators of wall ingrowth formation (Frontiers in Plant Physiology 4: 102). Exploiting this system, they've so far identified ‘master switches’ that respond to various inductive signals to co-ordinate wall ingrowth deposition in TCs. Ultimately, the hope is that manipulation of this process may provide new opportunities for improving crop yield. I'm sure we can all wish them well in that noble endeavour. And, if your appetite for TCs has now been whetted, these curious cells will feature in a future Research Topic in Frontiers of Plant Physiology to be edited by David McCurdy and Gregorio Hueros (http://bit.ly/18SShFr).
Image: Kelvin Song/Wikimedia Commons.
The repressive ER
Often over-shadowed by other organelles such as the nucleus, chloroplast or vacuole, the endoplasmic reticulum (ER) – ‘an organelle of cells in eukaryotic organisms that forms an interconnected network of membrane vesicles’ (http://en.wikipedia.org/wiki/Endoplasmic_reticulum) – is slowly revealing its secrets (John Runions; http://www.illuminatedcell.com/ER.html). As a major component of the cell's secretory pathway, the ER is intimately involved in protein synthesis via the ribosomes that are studded along its cytoplasmic surface (and which give rise to RER – rough endoplasmic reticulum). The process of protein synthesis is known as translation (http://en.wikipedia.org/wiki/Translation_%28biology%29) as it involves ‘translation’ of the message encoded in the m(essenger)RNA (which is itself made within the nucleus and carries the information for a particular protein originally contained within a gene in the cell's DNA). However, once made, the ‘proteins’ – strictly speaking they are polypeptides: protein is a name that should be reserved for the fully functional, final product – are often altered to produce the protein, a process called post-translational modification (http://en.wikipedia.org/wiki/Posttranslational_modification). Whilst the details are beyond the scope of this item, the controls over gene expression – which include transcription, mRNA processing, and translation (http://en.wikipedia.org/wiki/Gene_expression) – are numerous. But one such system uses micro-ribonucleic acids (miRNAs; http://en.wikipedia.org/wiki/MicroRNA), short-lengths of RNA that interact with mRNA thereby preventing its subsequent translation into protein (Kendal Hirschi, Trends in Plant Science 17: 123–125, 2012). Now, here's the take-home message: Shengben Li et al. have demonstrated that translation-inhibition activity by miRNAs occurs on the ER (Cell 53: 562–574, 2013), and requires ALTERED MERISTEM PROGRAM1 (AMP1), which encodes an integral membrane protein associated with ER. But! Not only is this study important in identifying a previously unknown function of the ER, the work was performed in arabidopsis (i.e. a plant!), and, according to Xuemei Chen (lead researcher of the work), ‘as AMP1 has counterparts in animals, our findings in plants could have broader implications’ (http://bit.ly/10lDhRi). How refreshing to see plant work paving the way for animal/biomed studies!
[For more on the world of small RNA, timely news that the Plant Cell's Teaching Tools in Plant Biology on that topic has just been revised. This FREE resource – which includes a ready-made PowerPoint presentation, lecture notes, and teaching guide – can be accessed at http://www.plantcell.org/site/teachingtools/TTPB5.xhtml. – Ed.]
Image: Magnus Manske/Wikimedia Commons.