Expression quantitative trait loci mapping identified PtrXB38 as a key hub gene in adventitious root development in Populus

Plant establishment requires the formation and development of an extensive root system with architecture modulated by complex genetic networks. Here, we report the identification of the PtrXB38 gene as an expression quantitative trait loci (eQTL) hotspot, mapped using 390 leaf and 444 xylem Populus trichocarpa transcriptomes. Among predicted targets of this trans-eQTL were genes involved in plant hormone responses and root development. Overexpression of PtrXB38 in Populus led to significant increases in callusing and formation of both stem-born roots and base-born adventitious roots. Omics studies revealed that genes and proteins controlling auxin transport and signaling were involved in PtrXB38-mediated adventitious root formation. Protein-protein interaction assays indicated that PtrXB38 interacts with components of endosomal sorting complexes required for transport machinery, implying that PtrXB38-regulated root development may be mediated by regulating endocytosis pathway. Taken together, this work identified a crucial root development regulator and sheds light on the discovery of other plant developmental regulators through combining eQTL mapping and omics approaches.

Endogenous salicylic acid suppresses de novo root regeneration from leaf explants

Plants can regenerate new organs from damaged or detached tissues. In the process of de novo root regeneration (DNRR), adventitious roots are frequently formed from the wound site on a detached leaf. Salicylic acid (SA) is a key phytohormone regulating plant defenses and stress responses. The role of SA and its acting mechanisms during de novo organogenesis is still unclear. Here, we found that endogenous SA inhibited the adventitious root formation after cutting. Free SA rapidly accumulated at the wound site, which was accompanied by an activation of SA response. SA receptors NPR3 and NPR4, but not NPR1, were required for DNRR. Wounding-elevated SA compromised the expression of AUX1, and subsequent transport of auxin to the wound site. A mutation in AUX1 abolished the enhanced DNRR in low SA mutants. Our work elucidates a role of SA in regulating DNRR and suggests a potential link between biotic stress and tissue regeneration.

Endomyocardial Biopsy via the Femoral Vein Using a Long, Curved Sheath

BACKGROUND

Endomyocardial biopsy (EMB) has been defined as the gold standard method for surveillance of rejection after heart transplantation, and it has also been used in the diagnosis of myocarditis and the unknown causes of cardiomyopathies. The procedure, however, is not free from complications. Access through the jugular vein or the femoral vein is the standard approach. In this study, we performed biopsies by using a long, curved sheath and evaluated the rate of complications with this technique.

METHODS

In this descriptive case series study, 97 EMBs were performed in 72 patients who were referred to a cardiovascular and medical research center in Tehran, Iran, between October 2011 and May 2013. The procedures were performed via the femoral approach by using a long bioptome with a long, curved sheath.

RESULTS

Adequate specimens were obtained in 97.9% of the total EMBs, with an average of 5 fragments per procedure. No deaths occurred, and there were no cases of pericardial effusion, myocardial rupture, papillary muscle rupture, increase in the severity of tricuspid regurgitation, atrioventricular block, sustained and nonsustained ventricular tachycardia, or atrial fibrillation. There was one case of persistent right bundle branch block.

CONCLUSIONS

Using a long, curved sheath can facilitate access to the interventricular septum compared with common sheaths and can be used safely in EMB via the femoral approach.