The era of nitric oxide in plant biology: Twenty years tying up loose ends.

Nitric oxide (NO) is an essential signal molecule to maintain cellular homeostasis in uni and pluricellular organisms. Conceptually, NO intervenes as much in sustaining basal metabolic processes, as in firing cellular responses to changes in internal and external conditions, and also in guiding the return to basal conditions. Behind these unusual capabilities of NO is the chemistry of this molecule, an unstable, reactive, free radical and short half-life gas. It is a lipophilic molecule that crosses all the barriers that biological membranes can impose. The extraordinary impact that the elucidation of physiological processes regulated by NO has had on plants, is comparable to the consequences of the discovery in 1986 that NO is present in animal tissues, and the following deep studies that demonstrated its biological activity regulating blood pressure. In this review, we have summarized and discuss the main discoveries that have emerged at Mar del Plata University over the past 20 years, and that have contributed to understand part of the biology of NO in plants. Besides, these findings are put in context with the progress made by other research groups, and in perspective, emphasizing that the history of NO in plants has just begun.

Multifunctional and Collaborative Protection of Proteins, Peptides, Phenolic Compounds, and Other Molecules against Oxidation in Apricot Seeds Extracts.

Antioxidant activity studies usually focus on a single type of molecule and do not consider possible collaborations among different molecules. The purpose of this work was to obtain multicomponent extracts exerting protection against oxidation from apricot seeds and to study the individual role of these components in the whole protection. Pressurized liquid extraction was employed to obtain extracts, and a response surface methodology enabled exploration of the effect of extraction conditions on the composition and prevalence of the antioxidant mechanism. Extractions carried out at 170 °C, in up to 7% ethanol, and for up to 25 min guaranteed multifunctional protection against oxidation by the collaboration of different molecules. While phenolic compounds were the main contributors to radical-scavenging capacity (R2 = 90% for ABTS and 88% for DPPH), proteins and phenolic compounds showed similar roles in the whole reducing power (proteins (R2 = 86%) and TPC (R2 = 90%)), and other compounds inhibited the formation of hydroxyl radicals and, especially, the peroxidation of lipids. The presence of peptides modified the antioxidant protection of extracts. UHPLC-Q-Orbitrap-MS/MS confirmed the presence of phenolic compounds and other antioxidant molecules. The presence of different kinds of molecules led to a multifunctional and collaborative protection against oxidation that could not be exerted by individual molecules.

Ectopic expression of mitochondrial gamma carbonic anhydrase 2 causes male sterility by anther indehiscence.

Plant mitochondria include gamma-type carbonic anhydrases (gammaCAs) of unknown function. In Arabidopsis, the gammaCAs form a gene family of five members which all are attached to the NADH dehydrogenase complex (complex I) of the respiratory chain. Here we report a functional analysis of gamma carbonic anhydrase 2 (CA2). The gene encoding CA2 is constitutively expressed in all plant organs investigated but it is ten fold induced in flowers, particularly in tapetal tissue. Ectopic expression of CA2 in Arabidopsis causes male sterility in transgenic plants. In normal anther development, secondary thickenings of the endothecial cell wall cause anthers to open upon dehydration. Histological analyses revealed that abnormal secondary thickening prevents anther opening in 35S::CA2 transgenic plants. CA2 abundance in transgenic plants is increased 2-3 fold compared to wild-type plants as revealed by Western blotting analyses. Moreover, abundance of other members of the CA family, termed CA3 and CAL2, is increased in transgenic plants. Oxygen uptake measurements revealed that respiration in transgenic plants is mainly based on NADH reduction by the alternative NADH dehydrogenases present in plant mitochondria. Furthermore, the formation of reactive oxygen species (ROS) is very low in transgenic plants. We propose that reduction in ROS inhibits H(2)O(2) dependent lignin polymerization in CA2 over-expressing plants, thereby causing male sterility.

Triassic actinopterygian fishes: the recovery after the end-Permian crisis.

In the last 15 years, the discovery of several new actinopterygian fish faunas from the Early and Middle Triassic of the Tethys, cast new light on the timing, speed and range of their recovery after the end-Permian crisis. In addition to several new taxa having been described, the stratigraphical and geographical record of many others have been greatly extended. In fact, most of the new fossiliferous sites are in southern China, thus at the Eastern end of the Tethys, and furthermore a few are somewhat older (Chaohu, Panxian, Luoping) than the major classical Western Tethys sites (Monte San Giorgio). Following these new finds, it is possible to have a better definition of the Triassic recovery stages. Indeed, after a quite short phase till the end of the Smithian (Olenekian, Early Triassic) in which a rather consistent fauna was present all around the Pangea coasts, a major radiation occurred in the Early-Middle Anisian after the new Middle Triassic fish fauna already appeared in the late Early Triassic, thus occuring well before what was previously supposed from the Alps localities. Furthermore, the new assemblages from southern China point to an early broader differentiation among the basal neopterygians rather than in the 'subholosteans', the group that was then dominant in the Western Tethys since the Late Anisian. It stands that during the Norian a new basal neopterygian radiation gave rise to several new branches that dominated the remaining part of the Mesozoic.

RETRACTED: Nitric oxide and flavonoids are systemically induced by UV-B in maize leaves.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of Cristina Lombardo, Lorenzo Lamattina, Raul Cassia. Several figures in the article by Tossi et al appear to have been intentionally manipulated and, therefore, representing results that are not accurate. The specific concerns are 1) the NO/-UVB panel in Fig. 1B is an apparent duplication of the Fig. 4 NO/PC panel; 2) the Flavonoid/UVB panel in Fig. 1B is an apparent duplication of the Fig. 4 Flavonoid/U panel; and 3), many of the RT-PCR bands in Fig. 5 are apparently identical. The apparent duplications of the panels in Fig. 1B and Fig. 4 appears to have been done intentionally. The brightness of the published Fig. 1B NO/-UVB panel was decreased and rotated 180 degrees relative to the NO/PC panel in Fig. 4. The two images are identical when the brightness of Fig. 1B is enhanced and the Fig. 4 panel rotated 180 degrees as shown in the attachment. Likewise, Fig. 1B Flavonoid/UVB panel was manipulated to disguise it from the Flavonoid/U panel in Fig. 4. We thank Dr Elisabeth Bik for drawing the irregularities to the authors' attention.

Unexpected localization of a lipid transfer protein in germinating sunflower seeds.

Plant lipid transfer proteins (LTPs) are low-molecular-mass proteins whose biological function still remains elusive. They are synthesized with a signal peptide that drives them to the secretory pathway. We have previously described the occurrence of an apoplastic LTP named Ha-AP10, present in sunflower seeds. Using a biochemical approach we now demonstrate that a fraction of Ha-AP10 is perispherically bound to membranes of germinating seeds. Purification of plasma membranes revealed the presence of Ha-AP10 in this fraction. Fluorimmunolocalization studies on germinating sunflower seeds demonstrated that in addition to the apoplastic and plasma membrane localization, Ha-AP10 is also present intracellularlly associated to unidentified structures. This varied distribution of Ha-AP10 in sunflower seeds may give novel clues to understand the role of LTPs in seed physiology.

Nitric oxide: an active nitrogen molecule that modulates cellulose synthesis in tomato roots.

Nitric oxide (NO) is a bioactive molecule involved in several growth and developmental processes in plants. These processes are mostly characterized by changes in primary and secondary metabolism. Here, the effect of NO on cellulose synthesis in tomato (Solanum lycopersicum) roots was studied. The phenotype of roots, cellulose content, the incorporation of 14C-glucose into cellulosic fraction and the expression of tomato cellulose synthase (CESA) transcripts in roots treated with the NO donor sodium nitroprusside (SNP) were analysed. Nitric oxide affected cellulose content in roots in a dose dependent manner. Low concentrations of SNP (pmoles of NO) increased cellulose content in roots while higher concentrations of SNP (nmoles of NO) had the opposite effect. This result correlated with assays of 14C-glucose incorporation into cellulose in roots. The effect of NO on 14C-glucose incorporation into cellulose was transient and reversible. Microscopic analysis of roots suggested that NO affected primary cell wall cellulose synthesis. Three tomato cellulose synthase (SICESA) transcripts were identified. Reverse transcriptase polymerase chain reaction experiments were carried out and indicated that SICESA1 and SICESA3 levels were affected by high NO concentrations. Together, these results support the hypothesis that variations in NO levels influence cellulose synthesis and content in roots.