Timothy E Gookin, Sarah M Assmann
We describe a previously unreported macroscopic Arabidopsis organ, the cantil, named for its 'cantilever' function of holding the pedicel at a distance from the stem. Cantil development is strongest at the first nodes after the vegetative to reproductive inflorescence transition; cantil magnitude and frequency decrease acropetally. Cantil expressivity is repressed by the specific heterotrimeric complex subunits GPA1, AGB1, and AGG3, which also play independent roles: GPA1 suppresses distal spurs at cantil termini, while AGB1 and AGG3 suppress ectopic epidermal rippling. These G protein mutant traits are recapitulated in long-day flowering gpa1-3 ft-10 plants, demonstrating that cantils, spurs, and ectopic rippling occur as a function of delayed phase transition, rather than as a function of photoperiod per se.
Multiseriate cortical sclerenchyma enhance root penetration in compacted soils
Hannah Schneider, Christopher Strock, Meredith Hanlon, Dorien Vanhees, Alden Perkins, Ishan Ajmera, Jagdeep Singh Sidhu, Sacha Mooney, Kathleen Brown, Jonathan Lynch
Genotypes with Multiseriate cortical sclerenchyma (MCS) had greater lignin concentration and bending strength at the root tip. In controlled environments, MCS in maize and wheat was associated with improved root tensile strength and increased penetration ability in compacted soils. Maize genotypes with MCS had root systems with 22% greater depth and 49% greater shoot biomass in compacted soils in the field compared to lines without MCS. Of the lines assessed, MCS was present in 30 to 50% of modern maize, wheat, and barley cultivars but was absent in teosinte and wild and landrace accessions of wheat and barley. MCS merits investigation as a trait for improving plant performance in maize, wheat, and other grasses under edaphic stress.
Plant defenses interact with insect enteric bacteria by initiating a leaky gut syndrome
Charles J. Mason, Swayamjit Ray, Ikkei Shikano, Michelle Peiffer, Asher G. Jones, Dawn S. Luthe, Kelli Hoover, and Gary W. Felton
Plants produce suites of defenses that can collectively deter and reduce herbivory. Many defenses target the insect digestive system, with some altering the protective peritrophic matrix and causing increased permeability. Plant physical and chemical defenses not only act directly upon the insect, but also have some interplay with the herbivore's microbiome. Combined direct and indirect, microbe-mediated assaults by maize defenses on the fall armyworm digestive and immune system reduced growth and elevated mortality in these insects. These results imply that plant-insect interactions should be considered in the context of potential mediation by the insect gut microbiome.
Compensatory sequence variation between trans-species small RNAs and their target sites
Nathan R Johnson, Claude W dePamphilis, Michael J Axtell
Trans-species small regulatory RNAs (sRNAs) are delivered to host plants from diverse pathogens and parasites and can target host mRNAs. How trans-species sRNAs can be effective on diverse hosts has been unclear. Multiple species of the parasitic plant Cuscuta produce trans-species sRNAs that collectively target many host mRNAs. Confirmed target sites are nearly always in highly conserved, protein-coding regions of host mRNAs. Cuscuta trans-species sRNAs can be grouped into superfamilies that have variation in a three-nucleotide period. These variants compensate for synonymous-site variation in host mRNAs. By targeting host mRNAs at highly conserved protein-coding sites, and simultaneously expressing multiple variants to cover synonymous-site variation, Cuscuta trans-species sRNAs may be able to successfully target multiple homologous mRNAs from diverse hosts.
Expansin gene loss is a common occurrence during adaptation to an aquatic environment
Nathan K. Hepler, Alexa Bowman, Robert E. Carey, Daniel J. Cosgrove
Expansins comprise a superfamily of plant cell wall loosening proteins that can be divided into four individual families (EXPA, EXPB, EXLA and EXLB). Aside from inferred roles in a variety of plant growth and developmental traits, little is known regarding the function of specific expansin clades, for which there are at least 16 in flowering plants (angiosperms); however, there is evidence to suggest that some expansins have cell‐specific functions, in root hair and pollen tube development, for example. The most convincing correlation between morphological reduction and expansin loss was seen for Utricularia and Spirodela, which both lack root hairs and the root hair expansin clade EXPA‐X. Contrary to the pattern observed in other species, four Utricularia expansins failed to branch within any clade, suggesting that they may be the result of neofunctionalization. Last, an expansin clade previously discovered only in eudicots was identified in Spirodela, allowing to conclude that the last common ancestor of monocots and eudicots contained a minimum of 17 expansins.