"Thylakoids of land plants have a bipartite structure, consisting of cylindrical grana stacks, made of membranous discs piled one on top of the other, and stroma lamellae which are helically wound around the cylinders.... Depending on light conditions, thylakoid membranes undergo dynamic structural changes that involve alterations in granum diameter and height, vertical unstacking of grana, and swelling of the thylakoid lumen. This plasticity is realized predominantly by reorganization of the supramolecular structure of protein complexes within grana stacks and by changes in multiprotein complex composition between appressed and non-appressed membrane domains."
Plants are constantly interpreting microbial signals from potential pathogens and potential commensals or mutualists. Because plants have no circulating cells dedicated to this task, every plant cell must, in principle, recognize any microbe as friend, foe, or irrelevant bystander. That tall order is mediated by an array of innate immune system receptors: pattern-recognition receptors outside the plant cell and nucleotide-binding oligomerization domain (NOD)–like receptors (NLRs) inside the cell. Despite their importance for plant health, how NLRs function mechanistically has remained obscure. On page 299 of this issue, Williams et al. (1) reveal a role for heterodimerization between NLRs and show how the rather limited NLR repertoire of any plant genome might be enhanced by combinatorial diversity.
Important Perspective from four heavy-hitters of US science (Bruce Alberts, Marc W. Kirschner, Shirley Tilghman, and Harold Varmus) = They call for a system that would " balance supply and demand in a sustainable fashion, adjust the pipeline that delivers new scientists, moderate the size of laboratories that are now difficult to fund, and restore an environment in which talented trainees and scientists can do their best work."
Mary Williams's insight:
One of their suggestions is to use more staff-level scientists in well-paid, permanent positions, rather than an endless stream of short-term postdocs. What do you think?
" In conclusion, we provide a method for developing large-scale induced mutation resources with relatively small investments that is applicable to resource-poor organisms. Furthermore, our results demonstrate that large libraries of sequenced mutations can be readily generated, providing enhanced opportunities to study gene function and assess the effect of sequence and chromatin context on mutations. "
Mary Williams's insight:
Nice paper and resouce for genetic studies in rice and wheat
Plant embryogenesis initiates with the establishment of an apical-basal axis; however, the molecular mechanisms accompanying this early event remain unclear. Here, we show that a small cysteine-rich peptide family is required for formation of the zygotic basal cell lineage and proembryo patterning in Arabidopsis. EMBRYO SURROUNDING FACTOR 1 (ESF1) peptides accumulate before fertilization in central cell gametes and thereafter in embryo-surrounding endosperm cells. Biochemical and structural analyses revealed cleavage of ESF1 propeptides to form biologically active mature peptides. Further, these peptides act in a non–cell-autonomous manner and synergistically with the receptor-like kinase SHORT SUSPENSOR to promote suspensor elongation through the YODA mitogen-activated protein kinase pathway. Our findings demonstrate that the second female gamete and its sexually derived endosperm regulate early embryonic patterning in flowering plants.
"We have revealed that apical dominance is predominantly controlled by the shoot tip’s intense demand for sugars, which limits sugar availability to the axillary buds. These findings overturn a long-standing hypothesis on apical dominance and encourage us to reevaluate the relationship between hormones and sugars in this and other aspects of plant development."
By Michael G. Mason, John J. Ross, Benjamin A. Babst, Brittany N. Wienclaw, and Christine A. Beveridge
In the fourth in a series of articles on Great British bioscience pioneers, Professor Ottoline Leyser at the University of Cambridge highlights advances in the understanding of plant developmental biology.
In developing nations, low soil nitrogen (N) availability is a primary limitation to crop production and food security, while in rich nations, intensive N fertilization is a primary economic, energy, and environmental cost to crop production. It has been proposed that genetic variation for root architectural and anatomical traits enhancing exploitation of deep soil strata could be deployed to develop crops with greater N acquisition. Here we provide evidence that maize (Zea mays L.) genotypes with few crown roots (crown root number: CN) have greater N acquisition from low N soils. Maize genotypes differed in their CN response to N limitation in greenhouse mesocosms and in the field. Low CN genotypes had 45% greater rooting depth in low N soils than high CN genotypes. Deep injection of 15N-labeled nitrate showed that low CN genotypes acquired more N from deep soil strata than high CN genotypes, resulting in greater photosynthesis and total nitrogen content. Under low N, low CN genotypes had greater biomass than high CN genotypes at flowering (85% in the field study in the US and 25% in South Africa). In the field in the US, 1.8x variation in CN was associated with 1.8x variation in yield reduction by N limitation. To our knowledge, this is the first report of the utility of CN for nutrient acquisition. Our results indicate that CN deserves consideration as a potential trait for genetic improvement of nitrogen acquisition from low N soils.
Cytoplasmic plant immune receptors recognize specific pathogen effector proteins and initiate effector-triggered immunity. In Arabidopsis, the immune receptors RPS4 and RRS1 are both required to activate defense to three different pathogens. We show that RPS4 and RRS1 physically associate. Crystal structures of the N-terminal Toll–interleukin-1 receptor/resistance (TIR) domains of RPS4 and RRS1, individually and as a heterodimeric complex (respectively at 2.05, 1.75, and 2.65 angstrom resolution), reveal a conserved TIR/TIR interaction interface. We show that TIR domain heterodimerization is required to form a functional RRS1/RPS4 effector recognition complex. The RPS4 TIR domain activates effector-independent defense, which is inhibited by the RRS1 TIR domain through the heterodimerization interface. Thus, RPS4 and RRS1 function as a receptor complex in which the two components play distinct roles in recognition and signaling.
Simon J. Williams, Kee Hoon Sohn, Li Wan, Maud Bernoux, Panagiotis F. Sarris, Cecile Segonzac, Thomas Ve, Yan Ma, Simon B. Saucet, Daniel J. Ericsson, Lachlan W. Casey, Thierry Lonhienne, Donald J. Winzor, Xiaoxiao Zhang, Anne Coerdt, Jane E. Parker, Peter N. Dodds, Bostjan Kobe, Jonathan D. G. Jones
"We found that the commonly used stress-inducing agents mannitol, sorbitol, NaCl and H2O2 impact shoot growth in a highly specific and dose-dependent way. Therefore, shoot growth is a sensitive, relevant and easily measured phenotype to assess stress tolerance over a wide range of stress levels."
Mary Williams's insight:
Often students use Arabidopsis seedlings in the teaching lab to learn about plant physiology. This paper shows that shoot growth is sensitive parameter to quantify even mild stress.
In this Special Issue, we have tried to capture the diversity of plant–microbe research that is on-going, and that might not normally be marketed under the banner of “plant microbiome research”. Nevertheless, it belongs under this banner and we highlight some of this research here, including a variety of plant “habitats” such as roots, leaves, and floral parts, as well as a variety of microbes, from bacteria and arbuscular mycorrhizal fungi to dark septate fungi. Of course, the field is broader than what we are able present in a single issue, but we hope that it inspires researchers of overlooked aspects of plant microbiota research to get in on the game, and contribute to a more complete picture of this complex “ecosystem”.
Plant phenology is known to depend on many different environmental variables, but soil microbial communities have rarely been acknowledged as possible drivers of flowering time. Here, we tested separately the effects of four naturally occurring soil microbiomes and their constituent soil chemistries on flowering phenology and reproductive fitness of Boechera stricta, a wild relative of Arabidopsis. Flowering time was sensitive to both microbes and the abiotic properties of different soils; varying soil microbiota also altered patterns of selection on flowering time. Thus, soil microbes potentially contribute to phenotypic plasticity of flowering time and to differential selection observed between habitats. We also describe a method to dissect the microbiome into single axes of variation that can help identify candidate organisms whose abundance in soil correlates with flowering time. This approach is broadly applicable to search for microbial community members that alter biological characteristics of interest.
It's always good to ask, "How does Physomitrella do this?"
"The moss Physcomitrella patens is part of an early divergent clade of land plants utilizing the plant hormone cytokinin for growth control. The rate-limiting step of cytokinin biosynthesis is mediated by isopentenyltransferases (IPTs), found in land plants either as adenylate-IPTs or as tRNA-IPTs. Although a dominant part of cytokinins in flowering plants are synthesized by adenylate-IPTs, the Physcomitrella genome only encodes homologues of tRNA-IPTs."
This is a nice short video that describes one approach to climate-proofing agriculture. There are lots of good ideas behind this project and it makes a good case study for students thinking about the diversity of farming methods as well as crops.
The miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) transcription factors function as an endogenous age cue in regulating plant phase transition and phase-dependent morphogenesis, but the control of SPL output remains poorly understood. InArabidopsis thaliana the spatial pattern of trichome is a hallmark of phase transition and governed by SPLs. Here, by dissecting the regulatory network controlling trichome formation on stem, we show that the miR171-targeted LOST MERISTEMS 1 (LOM1), LOM2 and LOM3, encoding GRAS family members previously known to maintain meristem cell polarity, are involved in regulating the SPL activity. Reduced LOM abundance by overexpression of miR171 led to decreased trichome density on stems and floral organs, and conversely, constitutive expression of the miR171-resistant LOM (rLOM) genes promoted trichome production, indicating that LOMs enhance trichome initiation at reproductive stage. Genetic analysis demonstrated LOMs shaping trichome distribution is dependent on SPLs, which positively regulate trichome repressor genes TRICHOMELESS 1 (TCL1) and TRIPTYCHON (TRY). Physical interaction between the N-terminus of LOMs and SPLs underpins the repression of SPL activity. Importantly, other growth and developmental events, such as flowering, are also modulated by LOM-SPL interaction, indicating a broad effect of the LOM-SPL interplay. Furthermore, we provide evidence that MIR171 gene expression is regulated by its targeted LOMs, forming a homeostatic feedback loop. Our data uncover an antagonistic interplay between the two timing miRNAs in controlling plant growth, phase transition and morphogenesis through direct interaction of their targets.