Genetic analysis of barrel field size in the first somatosensory area (SI) in inbred and recombinant inbred strains of mice

We measured the combined area of posterior medial barrel subfield (PMBSF) and anterior lateral barrel subfield (ALBSF) areas in four common inbred strains (C3H/HeJ, A?/J, C57BL?/6J, DBA/2J), B6D2F1, and ten recombinant inbred (RI) strains generated from C57BL/6J and DBA/2J progenitors (BXD) as an initial attempt to examine the genetic influences underlying natural variation in barrel field size in adult mice. These two subfields are associated with the representation of the whisker pad and sinus hairs on the contralateral face. Using cytochrome oxidase labeling to visualize the barrel field, we measured the size of the combined subfields in each mouse strain. We also measured body weight and brain weight in each strain. We report that DBA/2J mice have a larger combined PMBSF/ALBSF area (6.15?±?0.10?mm²,?n?=?7) than C57BL?/6J (5.48?±?0.13?mm²,?n?=?10), C3H/HeJ (5.37?±?0.16?mm²,?n?=?10), and A/J mice (5.04?±?0.09?mm²,?n?=?15), despite the fact that DBA/2J mice have smaller average brain and body sizes. This finding may reflect dissociation between systems that control brain size with those that regulate barrel field area. In addition, BXD strains (average n?=?4) and parental strains showed considerable and continuous variation in PMBSF/ALBSF area, suggesting that this trait is polygenic. Furthermore, brain, body, and cortex weights have heritable differences between inbred strains and among BXD strains. PMBSF/ALBSF pattern appears similar among inbred and BXD strains, suggesting that somatosensory patterning reflects a common plan of organization. This data is an important first step in the quantitative genetic analysis of the parcellation of neocortex into diverse cytoarchitectonic zones that vary widely within and between species, and in identifying the genetic factors underlying barrel field size using quantitative trait locus (QTL) analyses.     

Responses of photosynthetic properties and chloroplast ultrastructure of Bryum argenteum from a desert biological soil crust to elevated ultraviolet‐B radiation

Our understanding of plant responses to enhanced ultraviolet‐B (UV‐B) radiation has improved over recent decades. However, research on cryptogams is scarce and it remains controversial whether UV‐B radiation causes changes in physiology related to photosynthesis. To investigate the effects of supplementary UV‐B radiation on photosynthesis and chloroplast ultrastructure in Bryum argenteum Hedw., specimens were cultured for 10 days under four UV‐B treatments (2.75, 3.08, 3.25 and 3.41 W m^–2), simulating depletion of 0% (control), 6%, 9% and 12% of stratospheric ozone at the latitude of Shapotou, a temperate desert area of northwest China. Analyses showed malondialdehyde content significantly increased, whereas chlorophyll (Chl) fluorescence parameters and Chl contents decreased with increased UV‐B intensity. These results corresponded with changes in thylakoid protein complexes and chloroplast ultrastructure. Overall, enhanced UV‐B radiation leads to significant decreases in photosynthetic function and serious destruction of the chloroplast ultrastructure of B. argenteum. The degree of negative influences increased with the intensity of UV‐B radiation. These results may not only provide a potential mechanism for supplemental UV‐B effects on photosynthesis of moss crust, but also establish a theoretical basis for further studies of adaptation and response mechanisms of desert ecosystems under future ozone depletion.     

MAIGO2 is involved in abscisic acid‐mediated response to abiotic stresses and Golgi‐to‐ER retrograde transport

The central role of multisubunit tethering complexes in intracellular trafficking has been established in yeast and mammalian systems. However, little is known about their roles in the stress responses and the early secretory pathway in Arabidopsis. In this study, Maigo2 (MAG2), which is equivalent to the yeast Tip20p and mammalian Rad50‐interacting protein, is found to be required for the responses to salt stress, osmotic stress and abscisic acid in seed germination and vegetative growth, and MAG2‐like (MAG2L) is partially redundant with MAG2 in response to environmental stresses. MAG2 strongly interacts with the central region of ZW10, and both proteins are important as plant endoplasmic reticulum (ER)‐stress regulators. ER morphology and vacuolar protein trafficking are unaffected in the mag2, mag2l and zw10 mutants, and the secretory marker to the apoplast is correctly transported in mag2 plants, which indicate that MAG2 functions as a complex with ZW10, and is potentially involved in Golgi‐to‐ER retrograde trafficking. Therefore, a new role for ER–Golgi membrane trafficking in abiotic‐stress and ER‐stress responses is discovered.     

Enigmatic occurrence of Permian plant roots in Lower Silurian rocks,Guizhou Province,China

Pinnatiramosus qianensis Geng, 1986, is a plant with a complex, extensive pinnate branching system and pitted tracheids, collected from marine Lower Silurian (Llandovery; c. 430 Ma) rocks in Guizhou Province, China. It challenges long‐held theories on the origin and early evolution of vascular plants in the Silurian and Devonian. However, there is a hypothesis that the fossils were not syngenetic with the entombing rock, but were the rooting systems of much younger plants, probably of Permian age. New sections and collections of P. qianensis have been subjected to detailed analyses, which indicate that P. qianensis belongs to an early Permian (c. 285 Ma) rooting system growing down into lower Silurian rocks.     

Drought-induced H2O2 accumulation in subsidiary cells is involved in regulatory signaling of stomatal closure in maize leaves

Increasing H₂O₂ levels in guard cells in response to environmental stimuli are recently considered a general messenger involved in the signaling cascade for the induction of stomatal closure. But little is known as to whether subsidiary cells participate in the H₂O₂-mediated stomatal closure of grass plants. In the present study, 2-week-old seedlings of maize (Zea mays) were exposed to different degrees of soil water deficit for 3 weeks. The effects of soil water contents on leaf ABA and H₂O₂ levels and stomatal aperture were investigated using physiological, biochemical, and histochemical approaches. The results showed that even under well-watered conditions, significant amounts of H₂O₂ were observed in guard cells, whereas H₂O₂ concentrations in the subsidiary cells were negligible. Decreasing soil water contents led to a significant increase in leaf ABA levels associated with significantly enhanced O₂ ^? and H₂O₂ contents, consistent with reduced degrees of stomatal conductance and aperture. The significant increase in H₂O₂ appeared in both guard cells and subsidiary cells of the stomatal complex, and H₂O₂ levels increased with decreasing soil water contents. Drought-induced increase in the activity of antioxidative enzymes could not counteract the significant increase in H₂O₂ levels in guard cells and subsidiary cells. These results indicate that subsidiary cells participate in H₂O₂-mediated stomatal closure, and drought-induced H₂O₂ accumulation in subsidiary cells is involved in the signaling cascade regulating stomatal aperture of grass plants such as maize.     

Pepper osmotin-like protein 1 (CaOSM1) is an essential component for defense response, cell death, and oxidative burst in plants

Osmotin or osmotin-like protein, a PR-5 family member, is differentially induced in plants by abiotic and biotic stresses. Here, we demonstrate that the pepper (Capsicum annuum) osmotin-like protein 1 gene, CaOSM1, was required for the defense and hypersensitive cell death response and oxidative burst signaling during Xanthomonas campestris pv. vesicatoria (Xcv) infection. CaOSM1 protein was localized to the plasma membrane in leaf cells of Nicotiana benthamiana. Agrobacterium-mediated transient expression of CaOSM1 in pepper distinctly induced the hypersensitive cell death response and H₂O₂ accumulation. Knock-down of CaOSM1 in pepper by virus-induced gene silencing increased the susceptibility to Xcv infection, which was accompanied by attenuation of the cell death response and decreased accumulation of H₂O₂. CaOSM1 overexpression in transgenic Arabidopsis conferred reduced susceptibility and accelerated cell death response and H₂O₂ accumulation to infection by Pseudomonas syringe pv. tomato and Hyaloperonospora arabidopsidis. Together, these results suggest that CaOSM1 is involved in cell death and oxidative burst responses during plant defense against microbial pathogens.