Distéfano et al. show that an iron-dependent, oxidative cell death process with biochemical and morphological similarities to ferroptosis, as described in mammalian cells, has a physiological role in plants, regulating plant cell death in response to heat stress.

Stomatal closure is regulated by a complex network of signalling events involving numerous intermediates, among them nitric oxide (NO). Little is known about the signalling events occurring downstream of NO. Previous studies have shown that NO modulates cytosolic calcium concentration and the activation of plasma membrane ion channels. Here we provide evidence that supports the involvement of the lipid second messenger phosphatidic acid (PA) in NO signalling during stomatal closure. PA levels in Vicia faba epidermal peels increased upon NO treatment to maximum levels within 30 min, subsequently decreasing to control levels at 60 min. PA can be generated via phospholipase D (PLD) or via phospholipase C (PLC) in concerted action with diacylglycerol kinase (DGK). Our results showed that NO-induced PA is produced via the activation of both pathways. NO-induced stomatal closure was blocked either when PLC or PLD activity was inhibited. We have shown that PLC-and PLD-derived PA represents a downstream component of NO signalling cascade during stomatal closure.

Nitric oxide (NO) has recently emerged as a second messenger involved in the complex network of signaling events that regulate stomatal closure. Little is known about the signaling events occurring downstream of NO. Previously, we demonstrated the involvement of phospholipase D (PLD) in NO signaling during stomatal closure. PLDδ, one of the 12 Arabidopsis PLDs, is involved in dehydration stress responses. To investigate the role of PLDδ in NO signaling in guard cells, we analyzed guard cells responses using Arabidopsis wild type and two independent pldδ single mutants. In this work, we show that pldδ mutants failed to close the stomata in response to NO. Treatments with phosphatidic acid, the product of PLD activity, induced stomatal closure in pldδ mutants. Abscisic acid (ABA) signaling in guard cells involved H(2)O(2) and NO production, both required for ABA-induced stomatal closure. pldδ guard cells produced similar NO and H(2)O(2) levels as the wild type in response to ABA. However, ABA- or H(2)O(2)-induced stomatal closure was impaired in pldδ plants. These data indicate that PLDδ is downstream of NO and H(2)O(2) in ABA-induced stomatal closure.

The Apparent Paradox of ROSAs aerobic organisms, plants live in an oxygen rich environment. Inevitable, reactive oxygen species (ROS) by-products and their chemical reactions are part of their basic metabolism. Initially documented as a toxic consequence of aerobic metabolism, ROS can also work as signaling molecules regulating crucial developmental and physiological events in many different organisms. Plants, animals, and even fungi have evolved mechanisms in which ROS are used as messengers to fulfill an extensive range of key biological processes. In Drosophila melanogaster, a signaling role for ROS was demonstrated in the differentiation of common myeloid progenitors in hematopoietic cells. Previously considered as toxic by-products of aerobic metabolism, reactive oxygen species (ROS) are emerging as essential signaling molecules in eukaryotes. Recent evidence showed that maintenance of ROS homeostasis during female gametophyte development is crucial for embryo sac patterning and fertilization. Although ROS are exclusively detected in the central cell of mature embryo sacs, the study of mutants deficient in ROS homeostasis suggests that controlled oxidative bursts might take place earlier during gametophyte development. Also, a ROS burst that depends on pollination takes place inside the embryo sac. This oxidative response might be required for pollen tube growth arrest and for sperm cell release. in this mini-review, we will focus on new insights into the role of ROS during female gametophyte development and fertilization. Special focus will be made on the mitochondrial Mn-Superoxide dismutase (MSD1), which has been recently reported to be essential for maintaining ROS homeostasis during embryo sac formation.