7th Dec 2016

This weeks Arabidopsis Research Roundup is led by a study from the John Innes Centre in which Lars Ostergaard’s group identify a novel auxin-signaling module. Lars also kindly provides an audio description of this paper where we discuss the significance of this paper for our understanding of auxin signaling.

Secondly is a US-led paper that includes Sabrina Gonzalez-Jorge (University of Cambridge) as a co-author on a study that uses GWAS to identify novel loci involved in amino acid signalling.

Thirdly is a study from Keele University that uses Arabidopsis as an unlikely model for plant silica deposition. Lastly is a paper from the University of Sheffield that focusses on stomatal evolution in land plants.

Simonini S, Deb J, Moubayidin L, Stephenson P, Valluru M, Freire-Rios A, Sorefan K, Weijers D, Friml J, Østergaard L (2016) A noncanonical auxin-sensing mechanism is required for organ morphogenesis in Arabidopsis. Genes Dev. 30(20):2286-2296 Open Access

Lars Ostergaard (John Innes Centre) is the corresponding author of this pan-European project that defines a novel auxin-sensing mechanism. Our current understanding of this signaling module revolves around the auxin-mediated degradation of AuxIAA proteins that in turn leads to the derepression of Auxin Response Factor (ARF) transcription factors. This manuscript alters this paradigm by showing that the ARF3/ETTIN protein is able to independently sense auxin through interactions with process-specific transcription factors. This is important for coordinating a diverse range of developmental processes including gynoecium morphogenesis, lateral root emergence, ovule development, and primary branch formation, whereas disrupting these interactions lead to multiple growth defects. Therefore this manuscript provides insight into a novel mode of auxin signaling that might begin to help explain how auxin can mediate such a broad range of developmental processes.

Lars provides an audio description of this work.

Angelovici R, Batushansky A, Deason N, Gonzalez-Jorge S, Gore MA, Fait A, DellaPenna D (2016) Network-guided GWAS improves identification of genes affecting free amino acids. Plant Physiol. http:/​/​dx.​doi.​org/​10.​1104/​pp.​16.​01287 Open Access

Sabrina Gonzalez-Jorge (University of Cambridge) is a co-author on this US-led investigation that used genome-wide association studies (GWAS) techniques to identify new genes that are involved in the production of free amino acids (AAs). These AAs are not only used as protein building blocks but also act as important signaling molecules. In addition, during seed development these free AAs are an important source of energy. By performing GWAS analysis on hundreds of Arabidopsis ecotypes they identify a genomic region that contains two genes of note, namely the cationic amino acid transporter (CAT4) and a polynucleotide phosphorylase resistant to inhibition with fosmidomycin (RIF10). Cat4 mutant plants are deficient in Histidine-related growth processes and given the importance of this amino acid, this region is a prominent candidate for future biofortification strategies. Sabrina Gonzalez-Jorge will be chairing a session at next weeks GARNet Natural Variation Meeting to be held in Cambridge. Look out for the abstract book to be published on the GARNet website at the time of the meeting.

Brugiére T, Exley C (2016) Callose-associated silica deposition in Arabidopsis. J Trace Elem Med Biol. 39:86-90  http:/​/​dx.​doi.​org/​10.1016/j.jtemb.2016.08.005

This research paper comes from Chris Exley (Keele University) and results from an interest in the mechanism of silica deposition in the common Horsetail and whether this deposition occurs onto template of callose formation. It is known that plant pathogens induce callose deposition so in this study they used Arabidopsis mutants to assess whether induction of leaf callose formation in the presence of silicon could cause silica deposition. Indeed they show that callose deposition is coincident with silica accumulation but not in pmr4 mutant plants, which do not response to pathogen signal. Therefore they show that even though Arabidopsis is not a natural silica accumulator this response can be induced following callose deposition and offers a molecular insight into silicification of plants where this naturally occurs.

Chater CC, Caine RS, Tomek M, Wallace S, Kamisugi Y, Cuming AC, Lang D, MacAlister CA, Casson S, Bergmann DC, Decker EL, Frank W, Gray JE, Fleming A, Reski R, Beerling DJ (2016) Origin and function of stomata in the moss Physcomitrella patens Nat Plants. 2:16179


Researchers at the University of Sheffield lead this study in collaboration with colleagues in Leeds, Germany and the USA. They investigate the molecular factors that are required for stomatal development in the model basal land plant Physcomitrella patens. They show that two basic helix-loop-helix proteins PpSMF1 (SPEECH, MUTE and FAMA-like) and PpSCREAM1 (SCRM1) are essential for stomatal formation in moss and their function has been previously shown to rescued by their Arabidopsis orthologs. They show that these proteins function during sporophytic, but not gametophytic, development and in PpSMF1 and PpSCREAM1 mutants the lack of stomata result in delayed dehiscence, suggestive of a role for stomatal signaling in this process in early land plants.