New Insights on Plant Cell Elongation: A Role for Acetylcholine

We investigated the effect of auxin and acetylcholine on the expression of the tomato expansin gene LeEXPA2, a specific expansin gene expressed in elongating tomato hypocotyl segments. Since auxin interferes with clathrin-mediated endocytosis, in order to regulate cellular and developmental responses we produced protoplasts from tomato elongating hypocotyls and followed the endocytotic marker, FM4-64, internalization in response to treatments. Tomato protoplasts were observed during auxin and acetylcholine treatments after transient expression of chimerical markers of volume-control related compartments such as vacuoles. Here we describe the contribution of auxin and acetylcholine to LeEXPA2 expression regulation and we support the hypothesis that a possible subcellular target of acetylcholine signal is the vesicular transport, shedding some light on the characterization of this small molecule as local mediator in the plant physiological response

Endomembrane reorganization induced by heavy metals

Plant cells maintain plasmatic concentrations of essential heavy metal ions, such as iron, zinc, and copper, within the optimal functional range. To do so, several molecular mechanisms have to be committed to maintain concentrations of non-essential heavy metals and metalloids, such as cadmium, mercury and arsenic below their toxicity threshold levels. Compartmentalization is central to heavy metals homeostasis and secretory compartments, finely interconnected by traffic mechanisms, are determinant. Endomembrane reorganization can have unexpected effects on heavy metals tolerance altering in a complex way membrane permeability, storage, and detoxification ability beyond gene\u2019s expression regulation. The full understanding of endomembrane role is propaedeutic to the comprehension of translocation and hyper-accumulation mechanisms and their applicative employment. It is evident that further studies on dynamic localization of these and many more proteins may significantly contribute to the understanding of heavy metals tolerance mechanisms. The aim of this review is to provide an overview about the endomembrane alterations involved in heavy metals compartmentalization and tolerance in plants

Ipotesi sulla presenza di Glaucium flavum nel barocco leccese

Riassunto - Il barocco leccese si caratterizza per la ricca presenza di decorazioni vegetali, foglie, fusti e frutti. La tipica decorazione del capitello corinzio ha come elemento distintivo le foglie d’acanto. Per analogia con le decorazioni corinzie, molte altre foglie vengono definite “foglia d’acanto” pur non corrispondendo a tale pianta da un punto di vista anatomico. Sfruttando alcune caratteristiche botaniche, abbiamo identificato in molte decorazioni i tratti che riteniamo caratteristici della pianta tipica delle coste pugliesi Glaucium flavum Crantz comunemente noto come ‘papavero cornuto’. Se l’identificazione sarà confermata da valutazioni indipendenti, questa pianta potrebbe rappresentare un motivo decorativo estremamente ricorrente poiché parzialmente riprodotta in quasi ogni decorazione barocca del ‘700. L’importanza del riscontro di una pianta selvatica tipica degli ambienti salentini viene qui discussa

The Abscisic Acid–Related SNARE Homolog NtSyr1 Contributes to Secretion and Growth

Syntaxins and other SNARE proteins are crucial for intracellular vesicle trafficking, fusion, and secretion. Previously, we isolated the syntaxin-related protein NtSyr1 (NtSyp121) from tobacco in a screen for abscisic acid-related signaling elements, demonstrating its role in determining the abscisic acid sensitivity of K+ and Cl- channels in stomatal guard cells. NtSyr1 is localized to the plasma membrane and is expressed normally throughout the plant, especially in root tissues, suggesting that it might contribute to cellular homeostasis as well as to signaling. To explore its functions in vivo further, we examined stably transformed lines of tobacco that expressed various constructs of NtSyr1, including the full-length protein and a truncated fragment, Sp2, corresponding to the cytosolic domain shown previously to be active in suppressing ion channel response to abscisic acid. Constitutively overexpressing NtSyr1 yielded uniformly high levels of protein (>10 times the wild-type levels) and was associated with a significant enhancement of root growth in seedlings but not with any obvious phenotype in mature, well-watered plants. Similar transformations with constructs encoding the Sp2 fragment of NtSyr1 showed altered leaf morphology but gave only low levels of Sp2 fragment, suggesting a strong selective pressure against plants expressing this protein. High expression of the Sp2 fragment was achieved in stable transformants under the control of a dexamethasone-inducible promoter. Sp2 expression was correlated positively with altered cellular and tissue morphology in leaves and roots and with a cessation of growth in seedlings. Overexpression of the full-length NtSyr1 protein rescued the wild-type phenotype, even in plants expressing high levels of the Sp2 fragment, supporting the idea that the Sp2 fragment interfered specifically with NtSyr1 function by competing with NtSyr1 for its binding partners. To explore NtSyr1 function in secretion, we used a green fluorescent protein (GFP)-based section assay. When a secreted GFP marker was coexpressed with Sp2 in tobacco leaves, GFP fluorescence was retained in cytosolic reticulate and punctate structures. In contrast, in plants coexpressing secreted GFP and NtSyr1 or secreted GFP alone, no GFP fluorescence accumulated within the cells. A new yellow fluorescent protein-based secretion marker was used to show that the punctate structures labeled in the presence of Sp2 colocalized with a Golgi marker. These structures were not labeled in the presence of a dominant Rab1 mutant that inhibited transport from the endoplasmic reticulum to the Golgi. We propose that NtSyr1 functions as an element in SNARE-mediated vesicle trafficking to the plasma membrane and is required for cellular growth and homeostasis

Trafficking routes to the plant vacuole: connecting alternative and classical pathways

Due to the numerous roles plant vacuoles play in cell homeostasis, detoxification, and protein storage, the trafficking pathways to this organelle have been extensively studied. Recent evidence, however, suggests that our vision of transport to the vacuole is not as simple as previously imagined. Alternative routes have been identified and are being characterized. Intricate interconnections between routes seem to occur in various cases, complicating the interpretation of data. In this review, we aim to summarize the published evidence and link the emerging data with previous findings. We discuss the current state of information on alternative and classical trafficking routes to the plant vacuole

AtSYP51/52 show functional specificity in the post-Golgi traffic and act as i-SNAREs on tonoplast

Plant SNAREs coded by genes of the same family are generally considered as redundant in promoting vesicle-associated membrane fusion events. Nonetheless the application of innovative experimental approaches evidenced that members of the same gene family often have different functional specificities. The role of the two closely related Qc-SNAREs, the AtSYP51 and the AtSYP52 in the vesicle sorting to the central vacuole has been investigated. SYP5 proteins appeared to have functional specificity and to be part of a new functional class, the inhibitory SNAREs (i-SNAREs). When transiently over-expressed, the SYP51 and the SYP52 distributed between the TGN and the tonoplast. Our data demonstrate that these SYPs act as t-SNARE when present on the membrane of TGN/PVC, whereas they behave as i-SNARE when they accumulate on the tonoplast. A higher level of complexity emerges for functional classification of plant SNAREs

Le piante e la cura della salute

Sin dall’antichità, sappiamo che le piante hanno enormi potenzialità terapeutiche, oggi sempre più sfruttate. La ricerca si adopera proprio per approfondire la nostra conoscenza botanica a scopi medici e farmacologici