Arabidopsis Research Roundup: June 3rd 2015

We are unashamedly biased in this weeks Arabidopsis Research Roundup which firstly features work from the group of GARNet PI Jim Murray about the genetic interactions that define growth of lateral organs. Elsewhere we highlight papers that investigate a different role for CYCD3 genes in vascular development, the role of TFL1 in the shoot meristem and the ability of Arabidopsis seedling to tolerant a high light environment during ontogenesis.

Randall RS, Sornay E, Dewitte W, Murray JA (2015) AINTEGUMENTA and the D-type cyclin CYCD3;1 independently contribute to petal size control in Arabidopsis: evidence for organ size compensation being an emergent rather than a determined property Journal Experimental Botany http://dx.doi.org/10.1093/jxb/erv200

Jim Murray and Walter Dewitte (Cardiff) lead this study that investigates the relationship between the AINTEGUMENTA (ANT) transcription factor and cyclin CYCD3;1 during lateral aerial organ (LAO) formation. LAO growth is determined by the both the number and size of cells that comprise the organ. During petal development, ant mutants have reduced cell number but increased cell size, demonstrating a ‘compensatory mechanism’ of growth. In contrast cycd3;1 mutants have increased cell size that results in larger petals, showing no compensatory mechanism. Interestingly ant cycd3;1 double mutants do show growth compensation in the same tissue. The authors propose that occurrence of the compensatory mechanism depends on at which time-point during distinct phases of cell division and cell expansion the growth defect occurs.

 

C Collins, Maruthi M.N and C Jahn (2015) CYCD3 D-type cyclins regulate cambial cell proliferation and secondary growth in Arabidopsis. Journal Experimental Botany http://dx.doi.org/10.1093/jxb/erv218

Another study that investigates a different role of D-type cyclins is led by former Murray lab member, Carl Collins working at the Natural Resources Institute at the University of Greenwich. The factors that control cambial cell growth are poorly understood but the authors provide a link between the cell cycle and cambial differentiation by showing that CYCD3 subgroup of genes play a role in the process. Three CYCD3 genes are expressed in cambial tissue and the equivalent triple mutant has reduced hypocotyl and stem diameter, which is linked to a reduction in mitotic activity. Conversely, mutant xylem cells increased in size. This shows that CYCD3 genes provide a mechanism for controlling the correct proportions of cell growth during vascular development. This might provide a useful tool in the future study of this important process in woody plants.

 

Carvalho FE, Ware MA, Ruban AV (2015) Quantifying the dynamics of light tolerance in Arabidopsis plants during ontogenesis Plant Cell Environment http://dx.doi.org/10.1111/pce.12574

The group of Professor Alexander Ruban at Queen Marys University London utilise a novel methodology to measure the ‘intactness’ of photosystem II (PSII). In this paper they assess the amount of light required to inhibit PSII activity through the life cycle of Arabidopsis plants grown in short days. They show that maximum light tolerance occurs in 8-week old plants. Interestingly the light tolerance correlates with rates of electron transport yet did not coincide with the chlorophyll a/b ratios or anthocyanin content.

 

Baumann K, Venail J, Berbel A, Domenech MJ, Money T, Conti L, Hanzawa Y, Madueno F, Bradley D (2015) Changing the spatial pattern of TFL1 expression reveals its key role in the shoot meristem in controlling Arabidopsis flowering architecture. Journal Experimental Botany http://dx.doi.org/10.1093/jxb/erv247

The TFL1 gene is a repressor of flowering in the Arabidopsis shoot meristem. Researchers from the UK, USA, Spain and Italy, led by Desmond Bradley at the JIC show that ecoptocally expressed TFL1 can repress flowering outside of its normal expression domain. By comparing the expression of TFL1 with genes that determine floral identity (APETALA, LEAFY) the authors conclude that the shoot meristem is more sensitive to TFL1, allowing the maintenance of a vegetative state in this tissue.

Arabidopsis Research Round-up

There are three new and exciting Arabidopsis papers from the UK research community this week. The University of Bath makes two appearances, once with a Genetics paper, and once in collaboration with the University of Oxford in Genome Research. Representing Norwich this week, Jonathan Jones heads up a Sainsbury Lab/John Innes Centre collaboration to investigate simultaneous changes in gene expression between Arabidopsis and a pathogen.

 

  • Gnan S, Priest A and Kover PX. The genetic basis of natural variation in seed size and seed number and their trade-off using Arabidopsis thalianaMAGIC lines. Genetics, 13 October 2014. DOI: 10.1534/genetics.114.170746.

This team from the University of Bath explored the natural variation in genes affecting seed size and seed number in Arabidopsis. Both seed size and seed number were found to be affected by non-overlapping QTLs, therefore suggesting these two traits can evolve independently of each other. Trade-off between these two traits in terms of fecundity and yield is dependent upon life history traits.

 

  • Jiang C, Mithani A, Belfield EJ, Mott R, Hurst LD and Harberd NP. Environmentally responsive genome-wide accumulation of de novo Arabidopsis thaliana mutations and epimutations. Genome Research, 14 October 2014. DOI: 10.1101/gr.177659.114. [Open Access]

GARNet committee member Nick Harberd led on this Genome Research paper, along with co-corresponding author Caifu Jiang from China, and colleagues from theUniversity of Bath and Pakistan. In animal cells, repeated or prolonged presentation of a stressor often leads to increased mutations, which can increase the risk of cancer. Being sessile, plants do not get cancer in the same way that humans do, but do they acquire more mutations? Does stress – here the example of high soil salinity is used – drive the evolution of plants through increased phenotypic diversity? Yes, it seems so.

 

  • Asai S, Rallapalli G, Piquerez SJM, Caillaud M-C, Furzer OJ, Ishaque N, Wirthmueller L, Fabro G, Shirasu K and Jones JDG. Expression profiling during Arabidopsis/downy mildew interaction reveals a highly expressed effector that attenuates responses to salicylic acid. PLOS Pathogens, 16 October 2014. DOI: 10.1371/journal.ppat.1004443. [Open Access]

Led by Jonathan Jones, scientists from The Sainsbury Laboratory in Norwich worked with Lennart Wirthmueller from the John Innes Centre, and two Japanese collaborators, to produce this PLOS Genetics paper. Though gene expression patterns have been studied independently in the pathogen Hyaloperenospora arabidopsidis, and in its host Arabidopsis thaliana, they have not been compared simultaneously. Using a high-throughput cDNA tag sequencing method, this paper describes simultaneous changes in gene expression profiles in both host and pathogen.

New Methods and Resources (II)

Categories: methods
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Published on: February 12, 2013

As promised, here’s part two of my selection of recently published plant methods and resources.

Nisar et al. (2012; Plant Methods 8:50) present a method for easy inflorescence stem grafting in Arabidopsis. I can’t vouch for its ease, but the typical clear Plant Methods format provides plenty of description and comprehensive materials and methods section as well as a step-by-step guide to their customised wedge-cleft grafting technique. The authors even provide a table of technical tricks for each step in the protocol.

Abraham and Elbaum (2012; New Phyt. 197:1012-9) present a method of quantifying microfibril angle in secondary cell walls. The method is technical enough only to be of interest to researchers who need to know the angle of secondary cell wall microfibrils – this is not a look-see ‘Friday afternoon experiment,’ as my old supervisor used to say. To get a full picture, scanning electron microscopy, small-angle X-ray scattering, raman microspectroscopy should all be used in addition to the new technique, which is based on customised polarized light microscopy and LC-PolScope, an imaging software.

Cui et al. (2013; Plant Phys. 161: 36-47) demonstrate that the Tnt1 retrotransposon is a powerful tool for functional genomes in soybean. 62% of insertions from Agrobacterium-mediated transformations using a Tnt1 vector were into annotated genes, indicating the Tnt1 element preferentially inserts into protein-coding regions.  Multiple insertions occurred per transformation, and the transposons did not jump under normal growth conditions. The authors obtained the Tnt1 transposon from plasmid pHLV4909, which contains the entire sequence, and cloned it into the binary vector pZY101 for the transformations.

Developmental genetics with Zoe Wilson

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Published on: January 18, 2013

In the fourth of our series of video podcasts from PlantSci 2012, Zoe Wilson from the University of Nottingham discusses about her work on Arabidopsis developmental genetics. She works on pollen, which she explains is important for food security and the cut flower industry. Like the previous interviewees Eric, Katherine, and John, she also talks about the future of plant science. She says, “The link between plants and science had been quite tenuous, more people are understanding the importance of that.”

Identifying mutations in Arabidopsis – a faster, cheaper method


Highlighted paper: Liu, McCormack and Sheen (2012) Targeted parallel sequencing of large genonmic regions for identifying mutations in Arabidopsis. Plant Methods 8:12

Kun-hsiang Liu, Matthew McCormack and Jen Sheen from Harvard have developed a PCR-based method of identifying mutations in Arabidopsis. It is cheaper and easier than traditional methods of identifying mutations, using bench-top PCR and a new user-friendly method of bioinformatics analysis using web-based resource Galaxy. Liu et al. estimate that using their method to identify a mutation mapped to a 550kb genomic region will cost roughly US$500, a fraction of the usual ten thousand dollar cost of currently used methods of mutant identification.

Liu et al. tested the new method of identifying mutations by searching for new nitrogen response genes. They generated an Arabidopsis thaliana line in which LUCIFERASE was driven by the promoter for nitrogen response marker NIR. Using EMS-mutagenesis, the team made 25 000 mutant NIR:LUC lines and identified seedlings that were nitrate insensitive (nis) or showed nitrate constitutive response (ncr).

When the lines were made, the phenotypes were identified and a second generation was grown. Three second generation lines – ncr1, nis1 and nis2 – were selected for further investigation.

Liu et al. used their novel TPSeq method to locate the mutations causing the ncr1, nis1 and nis2 phenotypes. (more…)

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