Stomatal opening is induced by indoleacetic acid (IAA), cytokinins, and fusicoccin (FC), whereas stomatal closure is induced by abscisic acid (ABA). To test the effect of thes growth regulators on guard cell cytoslic Ca2+ ([Ca2+]k,) and pH (pHc.), epidermal strips were taken from the lower side of leaves of the orchid Paphiopedilum tonsum and were loaded with acetomethoxy-esterified forms ofthe Ca2+ indicator fluo-3 or the pH indicator 2',7'-bis(2-carboxyethyl)-5 (6) The opening and closure of stomatal pores, which regulate gas exchange in leaves, are associated with large changes in K+ levels in the guard cells (1). The K+ content of the guard cells is increased during stomatal opening (1), which is induced by light (2), low CO2 levels (3), humidity (4), indoleacetic acid (IAA) (5), fusicoccin (FC) (6), and cytokinins (7). Stomatal closure is associated with K+ release from the vacuoles and efflux across the plasma membrane (1), and closure can be induced by elevated levels of CO2 (2, 3), darkness (2), decreased humidity (2, 4), and abscisic acid (ABA) (8). It 1790The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Antibody-dependent cellular cytotoxicity (ADCC) is a major mechanism of action of therapeutic monoclonal antibodies (mAbs) such as cetuximab, rituximab and trastuzumab. Fc gamma receptors (FcgR) on human white blood cells are an integral part of the ADCC pathway. Differential response to therapeutic mAbs has been reported to correlate with specific polymorphisms in two of these genes: FCGR2A (H131R) and FCGR3A (V158F). These polymorphisms are associated with differential affinity of the receptors for mAbs. This review critically examines the current evidence for genotyping the corresponding single nucleotide polymorphisms (SNPs) to predict response to mAbs in patients with cancer.

BackgroundGuanylyl cyclases (GCs) catalyze the formation of the second messenger guanosine 3′,5′-cyclic monophosphate (cGMP) from guanosine 5′-triphosphate (GTP). Cyclic GMP has been implicated in an increasing number of plant processes, including responses to abiotic stresses such as dehydration and salt, as well as hormones.Principle FindingsHere we used a rational search strategy based on conserved and functionally assigned residues in the catalytic centre of annotated GCs to identify candidate GCs in Arabidopsis thaliana and show that one of the candidates is the brassinosteroid receptor AtBR1, a leucine rich repeat receptor like kinase. We have cloned and expressed a 114 amino acid recombinant protein (AtBR1-GC) that harbours the putative catalytic domain, and demonstrate that this molecule can convert GTP to cGMP in vitro.ConclusionsOur results suggest that AtBR1 may belong to a novel class of GCs that contains both a cytosolic kinase and GC domain, and thus have a domain organisation that is not dissimilar to that of atrial natriuretic peptide receptors, NPR1 and NPR2. The findings also suggest that cGMP may have a role as a second messenger in brassinosteroid signalling. In addition, it is conceivable that other proteins containing the extended GC search motif may also have catalytic activity, thus implying that a significant number of GCs, both in plants and animals, remain to be discovered, and this is in keeping with the fact that the single cellular green alga Chlamydomonas reinhardtii contains over 90 annotated putative CGs.

Phytosulfokines (PSKs) are sulfated pentapeptides that stimulate plant growth and differentiation mediated by the PSK receptor (PSKR1), which is a leucine-rich repeat receptor-like kinase. We identified a putative guanylate cyclase (GC) catalytic center in PSKR1 that is embedded within the kinase domain and hypothesized that the GC works in conjunction with the kinase in downstream PSK signaling. We expressed the recombinant complete kinase (cytoplasmic) domain of AtPSKR1 and show that it has serine/threonine kinase activity using the Ser/Thr peptide 1 as a substrate with an approximate K m of 7.5 M and V max of 1800 nmol min ؊1 mg ؊1 of protein. This same recombinant protein also has GC activity in vitro that is dependent on the presence of either Mg 2؉ or Mn 2؉ . Overexpression of the full-length AtPSKR1 receptor in Arabidopsis leaf protoplasts raised the endogenous basal cGMP levels over 20-fold, indicating that the receptor has GC activity in vivo. In addition, PSK-␣ itself, but not the non-sulfated backbone, induces rapid increases in cGMP levels in protoplasts. Together these results indicate that the PSKR1 contains dual GC and kinase catalytic activities that operate in vivo and that this receptor constitutes a novel class of enzymes with overlapping catalytic domains.

Dark-grown corn coleoptiles and parsley hypocotyls and their roots were loaded with acetoxymethyl esterified forms of the Ca21 indicator fluo-3, and the pH indicator 2',7'-bis(2-carboxyethyl)-5(and -6)-carboxyfluorescein. These tissues were treated with the plant growth regulator 2,4-dichlorophenoxyacetic acid (2,4-D) The plant growth regulators auxin (IAA; indoleacetic acid) and abscisic acid (ABA) influence plant development in a variety of ways. IAA, for example, promotes cell enlargement, cell division, vacuolar tissue differentiation, and tropistic responses (1). ABA enhances adaptation to various stresses and is involved in, for example, water regulation, photosynthate transport, and induction of seed storage protein synthesis (1, 2). ABA and IAA effects can be antagonistic. ABA inhibits IAA-induced cell elongation (3) and IAA can reverse the inhibitory effect of ABA on stomatal opening (4).Our work aims to identify the early messengers in IAA and ABA action. We found that application of IAA to corn coleoptiles led to rapid cytosolic acidification of epidermal cells (5). Acidification was monitored with a pH-sensitive microelectrode and was detectable <5 min after IAA was added. A decrease of :0. 1 pH unit occurred and the cytosolic pH (pHcy,) began to oscillate with a period of 20-30 min (5).Microelectrode studies showed IAA also rapidly increased cytosolic free Ca2+ ([Ca2+jcyt) levels, which oscillate with changes in pHcy, (6). The pHcy, decrease may be responsible for the increase in [Ca2+]CYt (7). We have found that increased[Ca2J ]cy and decreased pHcy, are spatially correlated with the localized increases in cell elongation associated with geoand phototropisms of corn coleoptiles (8). Stomatal closure is induced by ABA (4) and appears to be dependent on the availability of Ca2+ (9). However, no consistent effect on guard cell 45Ca2+ uptake was seen in response to ABA application (10). No response to ABA was seen in [Ca2J]cyt in root hairs injected by iontophoresis with the Ca2+ probe fura-2 (11). In contrast, ABA was shown to cause a transient increase in [Ca2+]cyt in guard cells prior to closure (12).In this paper, we use confocal scanning optical microscopy (CSOM) MATERIALS AND METHODS Plant Material. Zea mays (Terrific) seeds were soaked for 8-12 hr in tap water. They were then placed in moist vermiculite in a plastic box for 4-5 days at 26°C in the dark. The apical 3 mm of the coleoptile was removed, the following 10-20 mm was excised, and the primary leaves were removed. The coleoptile or roots were then cut into segments 1-4 mm long. Parsley (Petroselinum hortense) seeds were planted directly into a moist vermiculite/sand mixture (2:1) and incubated in the dark at 26°C for 6-9 days. Hypocotyls or roots were also cut in segments 2-4 mm long.