D.B. Pandit, cropping systems agronomist at CSISA-Bangladesh, shared with us this photo showing maize intercropped with red amaranth (a leaf vegetable widely used in Bangladesh) from the CSISA-Bangladesh demonstration plot in the Mymensingh hub.
Bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo), is not only a disease devastating rice production worldwide but also an ideal model system for studying the interaction between plants and their bacterial pathogens. The rice near-isogenic line (NIL) CBB23, derived from a cross between a wild rice Oryza rufipogon accession (RBB16) and a susceptible indica rice variety Jingang 30, is highly resistant to all field Xoo strains tested so far. Although the BB-resistance of CBB23 has been widely used in rice breeding programs, the mechanism of its extremely broad-spectrum resistance remains unknown. Here, we report the molecular cloning of an avirulence gene, designated as avrXa23, from Xoo strain PXO99A. We validate that AvrXa23, a novel transcription activator-like effector, specifically triggers the broad-spectrum BB-resistance in CBB23. Prevalence of avrXa23 in all 38 Xoo strains surveyed may explain the broad-spectrum feature of BB-resistance in CBB23. The results will significantly facilitate the molecular cloning of the corresponding R-gene in the host, and provide new insights into our understanding of molecular mechanism for broad-spectrum disease resistance in plants.
Grim. Science has exposed a thriving academic black market in China involving shady agencies, corrupt scientists, and compromised editors—many of them operating in plain view. The commodity: papers in journals indexed by Thomson Reuters' Science Citation Index, Thomson Reuters' Social Sciences Citation Index, and Elsevier's Engineering Index.
We've just uploaded revised files for TTPB19, Plants and their Microsymbionts (written with Ulrike Mathesius).
This lecture describes two very intimate symbiotic mutualisms: one is that which occurs between bacteria (rhizobia or Frankia) and their plant hosts resulting in the production of nitrogen-fixing nodules. The other is the interaction between two different types of mycorrhizal fungi and their plant hosts resulting in enhanced nutrient uptake. Successful formation of these mutualistic symbioses is a complex process that requires signaling and recognition, morphological and physiological responses, and biochemical contributions from both the plant and microsymbiont. Collectively these intimate alliances play a major role in nutrient assimilation by plants, and by extension, to humans and other animals.
Agrobacterium-mediated transformation is the most widely used technique for generating transgenic plants. However, many crops remain recalcitrant. We found that an Arabidopsis myb family transcription factor (MTF1) inhibited plant transformation susceptibility. Mutating MTF1 increased attachment of several Agrobacterium strains to roots and increased both stable and transient transformation in both susceptible and transformation-resistant Arabidopsis ecotypes. Cytokinins fromAgrobacterium tumefaciens decreased the expression of MTF1 through activation of the cytokinin response regulator ARR3. Mutating AHK3 and AHK4, genes that encode cytokinin-responsive kinases, increased the expression of MTF1 and impaired plant transformation. Mutant mtf1 plants also had increased expression of AT14A, which encodes a putative transmembrane receptor for cell adhesion molecules. Plants overexpressing AT14A exhibited increased susceptibility to transformation, whereasat14a mutant plants exhibited decreased attachment of bacteria to roots and decreased transformation, suggesting that AT14A may serve as an anchor point for Agrobacteria. Thus, by promoting bacterial attachment and transformation of resistant plants and increasing such processes in susceptible plants, treating roots with cytokinins may help engineer crops with improved features or yield.
La plus ca change... I was digging through the archives at Plant Physiology and found this report of a discussion from 1938 about "Teaching Methods in Plant Physiology".
Here's a sample: "Emphasis was placed on the shortage of enthusiasm for a complex subject like ours, and the usual difficulties in providing the expensive quarters and equipment for a relatively uninmportant elective course in a biology department." Link to PDF here: http://www.plantphysiol.org/content/13/4/873.full.pdf+html
The session was chaired by Charles A. Shull (pictured), editor-in-chief of Plant Physiology at the time
"Climate Change — The state of the science Produced by the International Geosphere-Biosphere Programme and Globaia and funded by the UN Foundation for the launch of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report"
Photosynthesis operates through a series of protein complexes that harvest sunlight and turn it into chemical energy. The separate complexes—including photosystems I and II, phycobilisome antennae, and reaction centers—are understood for a number of photosynthetic organisms; however, the large-scale organization and interactions between them are less clear. Using protein cross-linking, Liu et al. (p. 1104) demonstrate how the individual components are organized when present as a megacomplex in the cyanobacterium Synechocystis PCC 6803. Time-resolved fluorescence spectroscopy indicated that the phycobilisomes transfer energy to both photosystems, which is consistent with their molecular arrangement.
"Over the past two decades a growing body of empirical research has shown that many ecological processes are mediated by a complex array of indirect interactions occurring between rhizosphere-inhabiting organisms and those found on aboveground plant parts..."
Mary Williams's insight:
Intriguing! I like this perspective.
As the authors point out, "Unlike most terrestrial biota, the vast majority of plants occupy two connected “compartments”–the open air and soil– that differ in many biotic and abiotic properties. Aboveground plant structures include stems, branches, leaves, shoots, flowers, and seeds, whereas the soil is dominated by the root system. These differing plant structures facilitate interactions between biotic communities that rarely come into direct physical contact with one another".
I had to look up "Ampelography" - here's the definition I found, "the field of botany concerned with the identification and classification of grapevines".
Anyhow, it's a lovely paper looking at a combination of morphometric analysis of grape leaves from >1200 accessions, combined with mathematical analysis of shape and venation patterns, and finally with GWAS to look at the genetic basis of leaf shape. Fascinating work, and, of course, very applied (to preserve the interaction between genotype, environment and culture in grape and wine production).
The 25th July 2021 marks 400 years of botanical research and teaching by the University of Oxford...
"As a celebration and count-down to this anniversary, the University of Oxford Botanic Garden and Harcourt Arboretum, together with the Oxford University Herbaria and the Department of Plant Sciences, will highlight 400 plants of scientific and cultural significance.
From November 24th 2013, one plant will be profiled weekly, enabling you to see images associated with the plant from Oxford University's living and preserved collections."
From around 420 to 350 million years ago, when land plants were still the relatively new kids on the evolutionary block and “the tallest trees stood just a few feet high,” giant spires of life poked from the Earth. “The ancient organism boasted trunks up to 24 feet (8 meters) high and as wide as three feet (one meter),” said National Geographic in 2007. With the help of a fossil dug up in Saudi Arabia scientists finally figured out what the giant creature was: a fungus. (We think.)
How odd. My first thought was, "Where did it get its energy?". There's an intersting paper here that suggests that "non-vascular land plants or aquatic microbes were important contributors to its carbon sources" (based on carbon isotope analysis).
"Are there positions out there where science Ph.D.s can earn a good, secure living by teaching? Are there teaching-focused positions that include a professional salary, benefits, reasonable working conditions, and the equanimity that can come from job security? Do positions like that exist?"
Mary Williams's insight:
If you love teaching undergraduate students about science, read about these people who have made a good, secure career out of it. Gone are the days when teaching meant "second rate" ....
This is a great program if you are thinking you may want to get involved in science communication - application deadline 15 Jan 2014. The Fellowship is open to students who are ALREADY studying in the United States and who hold visas that allow them to receive payment for work during the 2014 summer.