Root cap specific expression of an endo-β-1,4--glucanase (cellulase): a new marker to study root development in Arabidopsis

The sloughing of root cap cells from the root tip is important because it assists the growing root in penetrating the soil. Using a promoter–reporter (GUS) and RT-PCR analysis, we identified an endo--1,4-glucanase (AtCel5) of Arabidopsis thaliana that is expressed exclusively in root cap cells of both primary and secondary roots. Expression is inhibited by high concentrations of IAA, both exogenous and internal, as well as by ABA. AtCel5 expression begins once the mature tissue pattern is established and continues for 3weeks. GUS staining is observed in both root cap cells that are still attached and cells that have already been shed. Using AtCel5-GUS as a marker, we observed that the root cap cells begin to separate at the sides of the tip while the cells of the central region of the tip separate last. Separation involves sequential tiers of intact cells that separate from the periphery of the root tip. A homozygous T-DNA insertion mutant that does not express AtCel5 forms the root cap and sheds root cap cells but sloughing is less efficient compared to wild type. The reduction in sloughing in the mutant does not affect the overall growth performance of the plant in loose media. The modest effect of abolishing AtCel5 expression suggests that there are multiple redundant genes regulating the process of sloughing of the root cap, including AtCel3/At1g71380, the paralog of the AtCel5 gene that is also expressed in the root cap cells. Thus, these two endo-1,4--d-glucanases may have a role in the sloughing of border cells from the root tip. We propose that AtCel5, provides a new molecular marker to further analyze the process of root cap cell separation and a root cap specific promoter for targeting to the environment genes with beneficial properties for plant growth.     

Restoring grassy woodland diversity through direct seeding: Insights from six ‘best‐practice’ case studies in southern Australia

Ecological restoration of grassy woodland ecosystems is now a significant landscape‐scale conservation objective throughout southern Australia. Technological improvements in direct seeding are now sufficiently well‐advanced to examine whether cost‐effective restoration of grassy woodlands is feasible. Consideration of six ‘best practice case studies shows substantial evidence of success. Further refinement of direct seeding techniques, in combination with native seed production systems, however, will be required into the future to meet the scale of woodland conservation targets and restore ecological function.     

Analysis of genetic diversity in a peatland specialist butterfly suggests an important role for habitat quality and small habitat patches

Understanding effects of habitat and landscape features on genetic variation is a prerequisite for the development of habitat and landscape management strategies aimed at conserving genetic diversity. While there has been considerable research on the effects of landscape structure on the genetics of populations, a recent review identified key biases in this body of work. The majority of landscape genetic studies investigate the intervening matrix’s influence on differentiation and gene flow among populations. Although characteristics of local habitat patches may be important determinants of genetic diversity, fewer studies have examined these relationships. Here we use node- and neighbourhood-based approaches to analyze correlates of genetic diversity in the bog copper (Lycaena epixanthe), a specialist butterfly endemic to temperate Nearctic peatlands that is threatened in parts of its range. Based on 190 repeatable and polymorphic amplified fragment length polymorphism loci, we found that genetic diversity was higher in habitat patches that were smaller and surrounded by more open water. Our results indicate that valuing small peatlands and preserving the surrounding water table may be important for conservation of genetic diversity in this highly specialized species. Our study highlights the importance of variables affecting habitat quality for conservation genetics.     

Linoleic acid and linolenic acid elongation products in muscle tissue of Syncerus caffer and other ruminant species

The metabolic elongation products of both linoleic acid and linolenic acid were found in muscle tissues of Syncerus caffer and other ruminants. The acids with four double bonds were predominantly in the linoleic acid series, whereas the higher degrees of unsaturation, mainly five double bonds, were in the linolenic acid series. The total linoleic acid and linolenic acid groups were present in the relative proportions of about 4:1, in contrast with the fish oils, where the acids are mainly in the linolenic acid series. The consistent occurrence of members of both groups of acids in the animals studied here suggests to us that both may be important for structural purposes.     

Specificity of reversible ADP-ribosylation and regulation of cellular processes

Proper and timely regulation of cellular processes is fundamental to the overall health and viability of organisms across all kingdoms of life. Thus, organisms have evolved multiple highly dynamic and complex biochemical signaling cascades in order to adapt and survive diverse challenges. One such method of conferring rapid adaptation is the addition or removal of reversible modifications of different chemical groups onto macromolecules which in turn induce the appropriate downstream outcome. ADP-ribosylation, the addition of ADP-ribose (ADPr) groups, represents one of these highly conserved signaling chemicals. Herein we outline the writers, erasers and readers of ADP-ribosylation and dip into the multitude of cellular processes they have been implicated in. We also review what we currently know on how specificity of activity is ensured for this important modification.