The starting point for this work was the idea that the 5’UTR of the core clock gene LATE ELONGATED HYPOCOTYL, also known as LHY, could function as a thermosensor given that we previously saw temperature sensitive alternative splicing of LHY.
We tested our theory using the 1001 genomes resource, a whole-genome sequence database for at least 1001 strains of the reference plant, Arabidopsis thaliana. Arabidopsis is native to Europe, but can now be found in the United States, North Africa and temperate Asia. We examined subtle differences, or polymorphisms, in the DNA sequences of >1001 accessions. These are often referred to as single nucleotide polymorphisms (SNPs). We found that different strains tended to ‘shake out’ as particular ordered assemblies of the SNPs, called haplotypes [for example, in the picture above the G/G/U/G/C haplotype is compared to the A/U/G/C/A haplotype] .
We were interested to see if the distinct haplotypes aligned with particular features of where these plants were growing – maybe the haplotypes grouped according to latitude, longitude, or altitude? Or would they group according to climate, such as temperature? seasonality? or even rainfall? For this we made use of the WorlClim database – a free public resource offering global climate data for ecological modelling.
The key findings were that:
One of the haplotypes has hallmarks of being a signature of ‘relict’ accessions (survivors of the last ice-age and the subsequent expansion of new populations). This version is the most distinct in the respect that, worldwide, the accessions bearing this haplotype are found in regions of low rainfall. They are also associated with the highest elevations with low mean annual temperatures and a wider range of maximum–minimum temperatures
Two of the remaining three haplotypes seem to associate with milder annual mean temperatures and lower altitude and wetter habitats
The fourth haplotype, seems to be a low temperature specialist. This haplotype is commonly found in the mountainous Pyrenees region of northern Spain and is prominent at the limit of Arabidopsis growth in northern Sweden
By measuring the extent of LHY spliced upon cooling in representative strains from two haplotypes we established that haplotype does indeed affect the splicing of LHY transcripts in response to cooling
We propose that the LHY haplotypes possess distinct 5′UTR pre‐mRNA folding thermodynamics and/or specific biological stabilities based around the binding of trans‐acting RNA splicing factors
There is much interest in identifying plant thermometers and how they have evolved to cope with new temperature environments. Our new work shows that subtle differences in the DNA sequence of global populations of Arabidopsis plants influences the scalable splicing sensitivity of the mRNA for this central clock component, thereby finely tuning the clock to specific temperature environments.
We anticipate that these findings will be of interest and relevant to crop breeding programs that aim to produce stable food crops in the face of changing climate.
Been growin’ the Arabidopsis seedlings in Eppendorf tubes filled with agar media. The young roots do what they do best and grow downwards through the agar media (this is called ‘gravitropism‘). The race is on though….if we don’t help them now they will be trapped in a plastic hell of diminishing nutrients.
That’s when we come to the rescue and clip the bottom of the agar tubes so that the growing roots can escape to freedom. This part of the process of growing Arabidopsis hydroponically is between the two earlier posts ‘Seed spotting‘ + ‘Green shoots emerging‘ and this later one: ‘Looking for roots‘. We use a tube cutter from VWR.
Once all the tubes are clipped, a puddle of hydroponic ‘root juice’ is added to the tray. This is double the strength of the hydroponic media used to make the agar in the tubes. We do this to help tease the roots down and out of the tube…it’s their reward for their escape to freedom.
Got a good crop this time…hopefully that’ll mean we can do lots of interesting experiments.
Lets have a look at how our little Arabidopsis plants are getting on. These were the plants that were growing in the yellow ‘nursery’ boxes. The young seedlings are about two weeks old, now growing hydroponically in blackened boxes to keep the roots dark.
Here, were having a wee look to see if the roots have emerged from the bottom of the cut Eppendorf tubes. Yes ! there are roots coming out into the hydroponic media (a minimal medium without any sucrose).
The boxes are in environmentally controlled growth cabinets (Sniggers cabinets) where we can control light intensity and temperature and humidity. I have the plants growing in 12 hours of light and 12 hours of dark (12h LD) at 20oC. These are quite standard “lab” conditions. I suppose 12h LD would be equivalent to the equinoxes in Nature…..would we ever get 20oC in Scotland in March or September ? (I very much doubt!)
Wow…talk about great minds thinking alike! Our blog, and research is also ‘about’…’time’.
Only we are all about circadian clocks and how plants tell the time.
Just how do plants anticipate the light at dawn for photosynthesis, and how do they time the breakdown of the starch that they’ve made during the day for surviving the dark of the night? How do they do this?
It’s their circadian clocks – molecular DNA and protein ‘cogs’ that link together to make a molecular timer. They just keep ticking – even during the night – maybe it even allows plants to ‘stay up all night to get lucky!’
Pretty funky, no?
We have circadian clocks too. Nile Rogers is an international jet set superstar. I’m sure he’ll feel his clock ‘squeal’ at times with all the globe trotting and jet lag. That’s when the internal clock becomes de-synchronised with its new environment, and it takes a day or two to readjust. Understanding circadian biology is a really ‘cool’ area of research just now. You only have to look at last years Nobel Prize for Physiology or Medicine – it went to circadian clock research!
All this funk makes me want to get down to our research song! Check it out here:
Thought that this was an interesting paper, published recently in PNAS.
The paper shows that alternative splicing produces different transcript isoforms for the 5’UTR region of the human gene encoding α-1-antitrypsin called SERPINA1, such that splicing of 5’UTR modulates the inclusion of long upstream ORFs (uORFs). What’s new with all this I hear you say. Well, the authors go on to show that while SERPINA1 transcripts produce the same protein isoform, they do so with different translation efficiencies. Differences in uORF content and 5’UTR secondary structure combine to differentiate the translational efficiencies of SERPINA1 transcripts.
α-1-antitrypsin is of interest because deficiencies in this protein are associated with chronic obstructive pulmonary disease (COPD), liver disease, and asthma. This work points to the possibility that genetic alterations in noncoding gene regions, such as the 5’UTR region, could result in α-1-antitrypsin deficiency.
The work also reinforces the idea that the amount of protein produced from a gene is not a simple function of the abundance of the transcript.
The reference is: Proc Natl Acad Sci U S A. 2017 Nov 21;114(47):E10244-E10253. doi: 10.1073/pnas.1706539114. Epub 2017 Nov 6.
The image used is their Figure 3. SHAPE-MaP structure probing data for SERPINA1 transcripts.
Loved the whimsical comedy of the ‘Detectorists‘ series with the excellent MacKenzie Crook (as Andy Stone) and Toby Jones (as Lance Stater). It follows Lance and Andy’s lives as their personal situations and ambitions orbit their central obsession with metal detecting.
It made me think of some analogies with Science. Obsession – yeah, tick. Do we ever stop thinking about our research topic? From hours of scanning the landscape only to uncover ‘ring-pull’ duds (yeah tick – see ‘failed experiments, no?). Or is it that we are just centimetres away from that Anglo-Saxon gold hoard. Maybe we have selected the wrong ‘field’ in the first place. I think that, like Lance and Andy, most of us dream of landing ‘the big one’ – maybe that discovery that will be transformative? We can but dream?
Especially loved the concept of the “discovery dance” – what kind of celebration would you do when the the game changing discovery comes your way….can you practice it? should you practice it?…or should it come as a natural reaction?
Here’s a link to a brief YouTube clip:
I think we are all Detectorists at heart. Think I’ll get practicing my dance….
After overfilling the tubes with the agar/growth media a cross is sliced into the agar with a sterile blade (see clip above). Doing this his will hopefully help the roots find a way down through the agar/growth media.
Then the Arabidopsis seeds (sterilised in bleach and suspended in sterile water) are pipetted onto the surface of the agar one-by-one (ok, maybe sometimes two-by two) – see clip below.
The trays are then sealed with micropore tape and that’s it – now to wait to see if the seeds germinate – should take around a week to see the emergence of the very young shoots.
Setting up the next experiment. It involves pipetting agar growth media into (literally) 100’s of tubes – see movie clip above. I try to overfill the tubes with the molten agar mixture (this is important for a later step….where I place single Arabidopsis seeds on the agar surface…watch this space).
Science is 99% perspiration, and 1% inspiration….and this is the ‘perspiration’ bit.