What We’re Reading: December 23

Short, accessible summaries of articles of broad interest to plant scientists, with links to the papers for more in-depth reading. Enjoy!

Review: Physics of pollinator attraction

pollinatorphysicsFlowers use a variety of strategies to attract pollinators and ensure successful pollination, including color and scent. Moyroud and Glover review some of the less familiar strategies including physical alterations to reflected light. As one example, conical epidermal cells on snapdragon flower petals focus and scatter light, enhancing petal coloration. Other petals appear glossy due to particularly flat epidermal cells, and still others have small structures that diffract light and so produce iridescence. The authors also describe floral tricks such as spring-loaded anthers that ensure pollen gets deposited onto the visiting pollinators. New Phytol. 10.1111/nph.14312 Tags: Biotic Interactions, Botany, Environmental Plant Biology

Review: Nuclear Ca2+ signaling in endosymbiosis

calciumThe Common Symbiosis Signaling Pathway (CSSP) conveys the perception of endosymbionts (rhizobia or mycorrhizal fungi) at the plasma membrane to the nucleus to initiate transcriptional responses. Calcium oscillations are core to the CSSP, whether the endosymbiont is fungal or bacterial. Barker et al. review the molecular players involved in the CSSP, with a focus on ongoing efforts to understand the contribution of calcium oscillations. They also describe new evidence that a third symbiotic partnership, that between Frankia bacteria and their actinorhizal plant partners, depends on the CSSP. New Phytol. 10.1111/nph.14350 Tags: Biotic Interactions, Botany, Signals and Responses

Review: Nitrogen sensing in legumes ($)

nodulenregulationAs a consequence of their ability to fix nitrogen in symbiosis with bacteria, legumes make key contributions to ecosystems and provide protein-rich foods for humans and other animals. Recent years have uncovered the nature of the signals involved in the cross-kingdom dialogues that occur between plant and bacteria and the systemic signals that optimize nodule activities. Murray et al. review nitrogen sensors and signals, as well as nitrate sensing through transceptors, peptide signals for N status in nodulation, and the contributions of hormones to nodule formation. Future research questions include the effect of N status on signaling between plant and bacteria and the influence of carbon / nitrogen imbalance on nodule activity. J. Exp. Bot.  10.1093/jxb/erw405 Tags: Biotic Interactions, Botany, Ecophysiology, Metabolism, Physiology, Signals and Responses

Reviews: Seed dormancy and germination ($)

germinationA pair of reviews in J. Exp. Bot. covers aspects of seed dormancy and germination. Steinbrecher and Leubner-Metzger (10.1093/jxb/erw428) provide an excellent introduction to materials science including stress-strain curves and Young’s Modulus, which they then apply to an understanding of the biophysics of seed germination. What happens when seeds imbibe water? How does the composition of seed tissues (embryo, endosperm, testa, pericarp) underpin the breaking of the seed coat by the emergence of the radicle? The review also explores the evolutionary history of seed biomechanics and its application towards the development of artificial seeds. Penfield and MacGregor (10.1093/jxb/erw436) start earlier in the process of seed development and review how the maternal environment, for example temperature, affects seed dormancy and germination. Mediators of such effects, including gene networks and hormones, are described. Tags: Abiotic Interactions, Botany, Cell Biology, Ecophysiology, Growth Regulation

Photosynthetic machinery protection induced by UV-B in Chlamydomonas

uvr8Light is good, too much light is bad. Photosynthetic organisms can dissipate excess light through a variety of means including non-photochemical quenching. Czechowski et al. show that in Chlamydomonas perception of UV-B light via the nuclear/cytosolic receptor UVR8 induces accumulation of proteins that contribute under high light conditions to non-photochemical quenching and the dissipation of excess light as heat. This study shows an example of anterograde signaling from the nucleus / cytosol to the plastid, and can contribute to efforts to improve crop efficiency through decreasing photoinhibition. Proc. Natl. Acad. Sci. USA 10.1073/pnas.1611567113 Tags: Abiotic Interactions, Biochemistry, Bioenergetics, Ecophysiology, Gene Regulation

Gene editing to produce doubly-determinate, early-yielding tomatoes ($)

determinatetomatoTomatoes have an indeterminate growth pattern that arises from the balance of flower-promoting (florigen) and flower repressing activities. Suppressing this flower-repressing activity leads to greater determinacy and facilitates cultivation. Soyk et al. compared flowering times in short- and long-days in close relatives of domesticated tomato, with a QTL analysis revealing two related genes, SFT (encoding florigen) and SP5G. Null alleles of SP5G, generated by CRISPR/Cas9, showed significantly earlier flowering in long days. Combining this with a mutation in the flower-repressing  SELF PRUNING (SP) gene led to even greater determinacy, translating to an early crop yield. This paper shows the potential of gene-editing to rapidly and specifically alter plant growth patterns and yields. Nature Genet. 10.1038/ng.3733 Tags: Applied Plant Biology, Development, Genetics, Growth Regulation

Evolution of fruit types in the Rosaceae family

fruitThe evolution of fruits might have been the most important feature that made angiosperms so successful. Fruits protect seeds and contribute to seed dispersal, as well as comprise a food source for humans and other animals, therefore, studying their evolution would help us shed light on the evolution of angiosperms themselves and also understanding their ecological implications. In their paper, Xiang et al. take us through their reconstruction of the Rosaceae family tree by using nuclear phenology after sequencing the transcriptomes of 123 species in this family (plus some outgroup species), and show us the importance of the role of whole genome duplications not only in speciation but also on the diversification of the family’s fruit types. (Summary by Gaby Auge) Mol. Biol Evol. 10.1093/molbev/msw242 Tags: Botany, Evolution, Genomics

Sub-Antarctic plants warm up themselves

articHigh latitude and altitude plants experience short growing seasons, consistent low temperatures, windy environments and unpredictable sunny spots. These plants are usually small and rely on self-pollination, but in Campbell, a Sub-Antarctic island, there are gardens of megaherbs that defy the predictions of what the flora should be according to the environment. Little et al. show that these megaherbs evolved large, corrugated and hairy leaves that keep the warmth in the boundary layer after brief sun exposure and, in addition, compact flowers with bright, dark colors that also stay warm and attract the few species of pollinators present in the island. Leaf and floral temperatures are correlated with light intensity and the mechanism by which the plants keep warmth don’t seem to be thermogenesis. This is also an excellent example of convergent evolution where flora of far away places (tropical alpine and Sub-Antarctic environments) developed similar structures to minimize damage by extreme cues and maximize metabolic rates. (Summary by Gaby Auge) Polar Research 10.3402/polar.v35.26030 Tags: Botany, Environmental Plant Biology, Evolution

History of Solanaceae family in genetic research

czerny_solanaceae-panel_12-21-16Plants from the Solanaceae family had, and continue to have, fundamental roles in plant genetic research.  Gebhardt summarizes the historical contributions of the Solanaceous plants tomato, tobacco, petunia, potato, pepper, and eggplant.  The tomato has been a model plant for studying fruit traits such as sugar content.  Fruit traits, including size, shape, and capsaicinoid content, have also been studied in the pepper plant, and the pepper has been useful for identifying resistance genes for bacterial and viral infections.  Tobacco was crucial for understanding regeneration of plants from undifferentiated cells and stable transformation using the Ti plasmid from Agrobacterium.  Petunia was used to study the genetics of flower morphology, pigmentation, and development.  The potato is uniquely suited for studying the genetics of tuber development, and the potato genome was useful for constructing genetic linkage maps to compare genome structures before the era of high-throughput sequencing.  The eggplant is an under-utilized Solanaceous plant, although a draft genome sequence was published in 2014.  The agronomic impact from the genetics of Solanaceous plants has come from identifying genes responsible for pathogen resistance and for desirable phenotypes, such as fruit color.  The Solanaceae family has central roles in both establishing plant genetics in the first half of the twentieth century and advancing plant genomics in recent decades. (Summary by Daniel Czerny) Theor. Appl. Genet. 10.1007/s00122-016-2804-1 Tags: Botany, Genetics, Genomics. Photo sources: ARS, Markus Hagenlocher, Aggie Horticulture, fir0002|flagstaffotos.com.au, فارس البلغمJoydeep

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