Auxology: when auxin meets plant evo-devo

Auxin is implicated throughout plant growth and development. Although the effects of this plant hormone have been recognized for more than a century, it is only in the past two decades that light has been shed on the molecular mechanisms that regulate auxin homeostasis, signaling, transport, crosstalk with other hormonal pathways as well as its roles in plant development. These discoveries established a molecular framework to study the role of auxin in land plant evolution. Here, we review recent advances in auxin biology and their implications in both micro- and macro-evolution of plant morphology. By analogy to the term 'hoxology', which refers to the critical role of HOX genes in metazoan evolution, we propose to introduce the term 'auxology' to take into account the crucial role of auxin in plant evo-devo.     

The nucleotide sequence, DNA damage location, and protein stoichiometry influence the base excision repair outcome at CAG/CTG repeats

Expansion of CAG/CTG repeats is the underlying cause of >14 genetic disorders, including Huntington's disease (HD) and myotonic dystrophy. The mutational process is ongoing, with increases in repeat size enhancing the toxicity of the expansion in specific tissues. In many repeat diseases, the repeats exhibit high instability in the striatum, whereas instability is minimal in the cerebellum. We provide molecular insights into how base excision repair (BER) protein stoichiometry may contribute to the tissue-selective instability of CAG/CTG repeats by using specific repair assays. Oligonucleotide substrates with an abasic site were mixed with either reconstituted BER protein stoichiometries mimicking the levels present in HD mouse striatum or cerebellum, or with protein extracts prepared from HD mouse striatum or cerebellum. In both cases, the repair efficiency at CAG/CTG repeats and at control DNA sequences was markedly reduced under the striatal conditions, likely because of the lower level of APE1, FEN1, and LIG1. Damage located toward the 5' end of the repeat tract was poorly repaired, with the accumulation of incompletely processed intermediates as compared to an AP lesion in the center or at the 3' end of the repeats or within control sequences. Moreover, repair of lesions at the 5' end of CAG or CTG repeats involved multinucleotide synthesis, particularly at the cerebellar stoichiometry, suggesting that long-patch BER processes lesions at sequences susceptible to hairpin formation. Our results show that the BER stoichiometry, nucleotide sequence, and DNA damage position modulate repair outcome and suggest that a suboptimal long-patch BER activity promotes CAG/CTG repeat instability.     

Temperatures from 4 to 15 °C are suitable for preserving the fertilizing capacity of stallion semen stored for 22 h or more in INRA96 extender

This study tested whether variable temperatures (from −0.5 to 15 °C) and air exposure could be used under laboratory and under field conditions to store stallion sperm diluted in extender INRA96 without loss of fertility. Experiment 1 (laboratory conditions) measured the effects of two 72 h storage conditions (5 °C with air vs. 15 °C without air). Experiment 2 (fixed field conditions) measured the effects of 22 h of storage without air in disposable containers maintained at four ambient temperatures (7 °C, 17 °C, 27 °C, 39 °C with semen at −0.5 °C to 3 °C, 4 °C to 7 °C, 8 °C to 10 °C, 12 °C to 15 °C, respectively). Per cycle pregnancy rate (PC) was measured after one artificial insemination (AI) in uterine body of 200 × 10⁶ total spermatozoa, 7 h (Experiment 1) or 17 h (Experiment 2) before ovulation. In Experiment 1, PC was similar for both conditions (60% (n = 40 cycles) vs. 63% (n = 40), respectively, 5 stallions × 8 cycles). Only velocity VCL and ALH were slightly higher at 15 °C. In Experiment 2, PC was reduced when ambient temperature was low (semen at −0.5 °C to 3 °C; PC = 25%) rather than intermediate (semen at 4 °C to 7 °C; PC = 53%) or high (semen at 8 °C to 10 °C; PC = 50%) (4 stallions × 8 cycles) (P = 0.002). Sperm stored at −0.5 °C to 3 °C had lower acrosome integrity/responsiveness, similar membrane integrity (HOS test) and motilities, and higher VCL and ALH, than semen stored between 4 and 15 °C. These results demonstrate a wide tolerance of equine sperm to variable positive temperatures and air exposure for 22 h storage and more. However, temperatures close to 0 °C are detrimental for fertility.     

Nanobacteria are mineralo fetuin complexes

"Nanobacteria" are nanometer-scale spherical and ovoid particles which have spurred one of the biggest controversies in modern microbiology. Their biological nature has been severely challenged by both geologists and microbiologists, with opinions ranging from considering them crystal structures to new life forms. Although the nature of these autonomously replicating particles is still under debate, their role in several calcification-related diseases has been reported. In order to gain better insights on this calciferous agent, we performed a large-scale project, including the analysis of "nanobacteria" susceptibility to physical and chemical compounds as well as the comprehensive nucleotide, biochemical, proteomic, and antigenic analysis of these particles. Our results definitively ruled out the existence of "nanobacteria" as living organisms and pointed out the paradoxical role of fetuin (an anti-mineralization protein) in the formation of these self-propagating mineral complexes which we propose to call "nanons." The presence of fetuin within renal calculi was also evidenced, suggesting its role as a hydroxyapatite nucleating factor.     

Investigation of host factors possibly enhancing the emergence of the chondroitin sulfate A-binding phenotype in Plasmodium falciparum

In malaria endemic areas, regardless of immunity acquired during lifelong exposure to malaria, pregnant women become susceptible to Plasmodium falciparum infections. Malaria during pregnancy is associated with a massive sequestration of infected erythrocytes in the placenta and the emergence of a unique parasite-derived adhesive molecule (encoded by var2CSA) that binds to chondroitin sulfate A (CSA). How P. falciparum achieves the timely expression of the CSA ligand in pregnant women remains puzzling. We investigated whether host serum-specific factors present only during pregnancy may induce var2CSA expression. Our panel of experiments did not reveal significant changes in var2CSA levels and CSA-binding capacity.     

Restoration of the jejunal mucosa in rats refed after prolonged fasting

To investigate the importance of body fuel depletion on gut rehabilitation after food deprivation, we compared the kinetics of jejunal mucosa alteration and restoration in rats that were refed after reaching different stages in body fuel depletion. Rats (P2) were refed while still in the so-called phase II, where body protein utilization is minimized, whereas rats (P3) were refed when they had reached the stage of increasing protein utilization (phase III). There was a significant decrease in total mass of intestine (P2, -30%; P3, -40%) and jejunal mucosa (P2, -52%; P3, -60%), as well in the size of the crypts (P2, -15%; P3, -36%) and villi (P2, -37%; P3, -55%). Structural changes of the mucosa included disappearance of some villi and a reduction in the size and number of crypts. Despite the larger morphological alterations in P3, the restoration of mucosa was as fast and complete after only 3 days of refeeding for both P2 and P3 rats. The respective roles of the mitosis pressure and of the lamina propria dynamics were studied. The rapid reversibility of the gut mucosal alterations due to fasting might constitute an integrative process.     

The first transepidermal transplantation of non‐cultured epidermal suspension using a dermarolling system in vitiligo: A sequential histological and clinical study

The current methods for melanocyte delivery to depigmented skin are invasive and often require sophisticated approaches. Here, we describe a promising simple and minimally invasive technique based on the dermarolling system. The technique involves preparation of a keratinocyte/melanocyte suspension prepared by trypsinization from a non‐lesioned part of a patient's scalp skin and transepidermal delivery using a dermaroller equipped with 0.2‐mm needles. Dermarolling leads to epidermal microinjuries without, however, causing pain or inflammation. The technique was applied to facial depigmented areas of five patients with stable vitiligo that were resistant to conventional UV/tacrolimus treatment. The efficacy of cell delivery was analysed histologically on punch biopsies, and repigmentation was evaluated photographically and by clinical assessment. We found that the transplanted keratinocytes rapidly degenerated, leading to keratinization, but melanocytes survived and integrated appropriately into the basal layer of the epidermis, leading to excellent repigmentation after 6 months in three cases and mild repigmentation in two cases. Although based on a small number of patients, we anticipate this technique to become a valid addition to the arsenal of therapeutic approaches to repigmentation in depigmenting disorders.     

Synthesis and physicochemical characterization of oxo and phenylimido Re(V), Re(III) and Ni(II) complexes with the 2-[bis(ethoxyethyl)phosphino]phenolato ligand and derivatives

2-[Bis(ethoxyethyl)phosphino]phenol P¹-OH reacts in basic refluxing solvents with ReOCl₃(PPh₃)₂, in a 2/1 molar ratio, to give the green ReOCl(P¹-O)₂ complex. Structure elucidation by ³¹P NMR is consistent with a cis-PP “twisted” octahedral complex, which is the preferred conformation on electronic grounds. The complex is unique in toluene while several species were present in ethanol. When the reaction is performed with Re(NPh)Cl₃(PPh₃)₂, a mixture of trans-PP (major) and cis-PP(minor) species in a 3/1 ratio is obtained. These geometric isomers were distinguished by their ²J_PP coupling constants. Only cis-PP-Re(NPh)Cl(P¹-O)₂, less soluble, could be isolated and its molecular structure determined by physicochemical measurements. This is the first example of cis-PP phosphinophenolato complex with the [ReNPh]³⁺ core, thus illustrating the importance of the steric demand of the phosphine substituent. Reaction of P¹-OH with NiCl₂ gives Ni(P¹-O)₂ as an orange oily solid with a cis-PP square planar structure. This structure is the most probable based on the ³¹P, ¹³C NMR data.     

The Human Obesity Gene Map: The 2003 Update

This is the tenth update of the human obesity gene map, incorporating published results up to the end of October 2003 and continuing the previous format. Evidence from single‐gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome‐wide scans and animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. Transgenic and knockout murine models relevant to obesity are also incorporated (N = 55). As of October 2003, 41 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. QTLs reported from animal models currently number 183. There are 208 human QTLs for obesity phenotypes from genome‐wide scans and candidate regions in targeted studies. A total of 35 genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 272 studies reporting positive associations with 90 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, more than 430 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http:obesitygene.pbrc.edu .     

One for all and all for one: the energetic benefits of huddling in endotherms

Huddling can be defined as “an active and close aggregation of animals”. It is a cooperative group behaviour, permitting individuals involved in social thermoregulation to minimize heat loss and thereby lower their energy expenditure, and possibly allowing them to reallocate the saved energy to other functions such as growth or reproduction. Huddling is especially important in the case of animals faced with high heat loss due to a high surface‐to‐volume ratio, poor insulation, or living in cold environments. Although numerous experimental studies have focused on the huddling behaviour of a wide range of species, to our knowledge, this is the first attempt to review the various implications of this widely used behavioural strategy. Huddling allows individuals to maximise energy savings by (1) decreasing their cold‐exposed body surface area, (2) reducing their heat loss through warming of ambient temperatures surrounding the group, and (3) eventually lowering their body temperature through physiological processes. Huddling provides substantial energy savings and is estimated to reduce energy expenditure by between 6 and 53%. Broad variations in the energetic benefits of huddling depend on the number of individuals and species involved in huddles, the ambient temperatures to which individuals are exposed and the density of the aggregations. It has been shown that huddling individuals have increased survival, a lower food intake, a decreased body mass loss, increased growth rate, reduced water loss, and/or a more constant body temperature together with a significant reduction in metabolic rate. Though huddling has been studied widely, this review reveals the intricacies of this adaptive behaviour.