Ricerc@Sapienza

In Arabidopsis basal hypocotyls of dark-grown seedlings, xylary cells may form from the pericycle as an alternative to adventitious roots. Several hormones may induce xylogenesis, as Jasmonic acid (JA), as well as indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) auxins, which also affect xylary identity. Studies with the ethylene (ET)-perception mutant ein3eil1 and the ET-precursor 1-aminocyclopropane-1-carboxylic acid (ACC), also demonstrate ET involvement in IBA-induced ectopic metaxylem.

In basal hypocotyls of dark-grown Arabidopsis seedlings, xylary cells may form from the pericycle as an alternative to another developmental program, i.e. adventitious roots. It is known that several hormones may induce xylogenesis, as jasmonic acid (JA), indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA), which also affect xylary cell identity. Recent studies with the ethylene (ET)-perception mutant ein3eil1 and the ET-precursor 1-aminocyclopropane-1-carboxylic acid (ACC) have shown ET involvement in IBA induced ectopic metaxylem.

Oryza sativa L. is a worldwide food-crop frequently growing in cadmium (Cd)/arsenic (As) polluted soils, with its root-system as the first target of the pollutants. Root-system development involves the establishment of optimal indole-3-acetic acid (IAA) levels, also requiring the conversion of the IAA natural precursor indole-3-butyric acid (IBA) into IAA, causing nitric oxide (NO) formation. Nitric oxide is a stress-signaling molecule. In rice, a negative interaction of Cd or As with endogenous auxin has been demonstrated, as some NO protective effects.

Nitric oxide (NO) has signalling roles in plant stress responses. Cadmium (Cd) and arsenic (As) soil pollutants alter plant development, mainly the root-system, by increasing NO-content, triggering reactive oxygen species (ROS), and forming peroxynitrite by NO-reaction with the superoxide anion. Interactions of NO with ROS and peroxynitrite seem important for plant tolerance to heavy metal(oid)s, but the mechanisms underlying this process remain unclear.

In plant cells, cadmium (Cd) and arsenic (As) exert toxicity mainly by inducing oxidative stress through an imbalance between the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS), and their detoxification. Nitric oxide (NO) is a RNS acting as signalling molecule coordinating plant development and stress responses, but also as oxidative stress inducer, depending on its cellular concentration.

This editorial refers to ‘Hypertension and increased endothelialmechanical stretch promotemonocyte differentiation and activation: roles of STAT3, interleukin 6 and hydrogen peroxide’ by R. Loperena et al., pp. 1547–1563.