Ziziphus joazeiro Mart., popularly known as “juazeiro”, is a tree widely found in the northeast of Brazil. It is commonly used as an anti-inflammatory, antibacterial, antifungal, and analgesic agent. The stem extract exhibited, beside cytotoxic properties, substantial activity against the Gram-negative bacterium Allivibrio fischeri. UHPLC-ESI-Orbitrap-HR-MS analysis of the alkaloidal fraction of the crude methanolic stem extract of this species enabled the detection and putative identification of sixteen cyclopeptide alkaloids (CPAs), including four possibly new structures. According to the MS2 fragmentation analysis, from the sixteen identified CPAs, three possess a type-Ia1, one a type-Ia2, and twelve a type-Ib cyclopeptide alkaloid core. The structures of paliurine-C and -D were supported by NMR data.

Calcium (Ca2+) ions play pivotal roles as second messengers in intracellular signal transduction, and coordinate many biological processes. Changes in intracellular Ca2+ levels are perceived by Ca2+ sensors such as calmodulin (CaM) and CaM-like (CML) proteins, which transduce Ca2+ signals into cellular responses by regulation of diverse target proteins. Insights into molecular functions of CaM targets are thus essential to understand the molecular and cellular basis of Ca2+ signaling. During the last decade, IQ67-domain (IQD) proteins emerged as the largest class of CaM targets in plants with mostly unknown functions. In the March issue of Plant Physiology, we presented the first comprehensive characterization of the 33-membered IQD family in Arabidopsis thaliana. We showed, by analysis of the subcellular localization of translational green fluorescent protein (GFP) fusion proteins, that most IQD members label microtubules (MTs), and additionally often localize to the cell nucleus or to membranes, where they recruit CaM Ca2+ sensors. Important functions at MTs are supported by altered MT organization and plant growth in IQD gain-of-function lines. Because IQD proteins share structural hallmarks of scaffold proteins, we propose roles of IQDs in the assembly of macromolecular complexes to orchestrate Ca2+ CaM signaling from membranes to the nucleus. Interestingly, expression of several IQDs is regulated by auxin, which suggests functions of IQDs as hubs in cellular auxin and calcium signaling to regulate plant growth and development.

Chirita drakei Burtt (now accepted as Primulina drakei (B.L.Burtt) Mich.Möller & A.Weber) is growing on limestone mountain slopes of Ha Long Bay islands in Vietnam. The chemical investigation of the aerial parts of C. drakei led to the isolation and structural elucidation of two new compounds named chiridrakoside A (1) and chiridrakoside B (2) besides twelve known compounds comprising five phenylethanoid glycosides (3–7), two lignans (8, 9), a phenyl propanoid (10), an anthraquinone (11), a furan derivative (12) and two triterpenes (13, 14). All described compounds, except 4, 5 and 11, were obtained for the first time from the genera Chirita or Primulina. The cytotoxic activity of the isolated compounds was evaluated against the four human cancer cell lines KB (mouth epidermal carcinoma), HepG2 (hepatocellular carcinoma), Lu (lung carcinoma) and MCF7 (breast carcinoma). Epoxyconiferyl alcohol (10) exhibited cytotoxic activity against the tested cell lines (IC50 from 46 to 128 μM).

Rothmannia talbotii, a hitherto chemically unexplored medicinal plant, is used in the Western Region of Cameroon to relieve fever. In our ongoing search for bioactive compounds from Cameroonian medicinal plants, a previously undescribed compound rothtalazepane (1), along with six known compounds, aitchisonide B (2), D-mannitol (3), β-D-glucopyranosyl-(6→1’)-β-D-glucopyranoside (4), monopalmitin (5), stigmasterol (6), and sitosterol 3-O-β-D-glucopyranoside (7) were isolated and characterized from the crude ethanol extract of the wood of R. talbotii. Rothtalazepane (1) exhibits no significant activity against several microbial strains, thus its function likely lies not in antimicrobial defense and it is not the active principle against urinary infections described for Rothmannia.

Four new 19-residue peptaibols, named tulasporins A–D (1–4), were isolated from the semi-solid cultures of Sepedonium tulasneanum. Their structures were elucidated on the basis of extensive ESI-HRMSn fragmentation studies as well as 1H NMR spectroscopic analyses. Interestingly, the structures of tulasporins A–D (1–4) resemble those of chrysospermins isolated earlier from cultures of S. chrysospermum. Previously, it was hypothesized that the peptaibol production by Sepedonium species correlates with the morphology of the aleurioconidia, as exclusively round-shaped aleurioconidia forming species produced peptaibols. Since the investigated Sepedonium tulasneanum produces oval aleurioconidia, this study can be considered as the first report of peptaibols from a Sepedonium strain with oval-shaped aleurioconidia. Thus, it could be demonstrated that both round as well as oval aleurioconidia forming Sepedonium species are able to produce peptaibols. Tulasporins A-D (1–4), when tested against phytopathogenic fungi, exhibited good growth inhibitory activity against both Botrytis cinerea and Phytophthora infestans, while they were devoid of significant activity against Septoria tritici.

Expression takes place for most of the jasmonic acid (JA)-induced genes in a COI1-dependent manner via perception of its conjugate JA-Ile in the SCFCOI1-JAZ co-receptor complex. There are, however, numerous genes and processes, which are preferentially induced COI1-independently by the precursor of JA, 12-oxo-phytodienoic acid (OPDA). After recent identification of the Ile-conjugate of OPDA, OPDA-Ile, biological activity of this compound could be unequivocally proven in terms of gene expression. Any interference of OPDA, JA, or JA-Ile in OPDA-Ile-induced gene expression could be excluded by using different genetic background. The data suggest individual signaling properties of OPDA-Ile. Future studies for analysis of an SCFCOI1-JAZ co-receptor-independent route of signaling are proposed.

AvrRpt2 is one of the first Pseudomonas syringae effector proteins demonstrated to be delivered into host cells. It suppresses plant immunity by modulating auxin signaling and cleavage of the membrane-localized defense regulator RIN4. We recently uncovered a novel potential virulence function of AvrRpt2, where it specifically blocked activation of mitogen-activated protein kinases, MPK4 and MPK11, but not of MPK3 and MPK6. Putative AvrRpt2 homologs from different phytopathogens and plant-associated bacteria showed distinct activities with respect to MPK4/11 activation suppression and RIN4 cleavage. Apart from differences in sequence similarity, 3 of the analyzed homologs were apparently “truncated.” To examine the role of the AvrRpt2 N-terminus, we modeled the structures of these AvrRpt2 homologs and performed deletion and domain swap experiments. Our results strengthen the finding that RIN4 cleavage is irrelevant for the ability to suppress defense-related MPK4/11 activation and indicate that full protease activity or cleavage specificity is affected by the N-terminus.

Out of the 34 members of the VQ-motif-containing protein (VQP) family, 10 are phosphorylated by the mitogen-activated protein kinases (MAPKs), MPK3 and MPK6. Most of these MPK3/6-targeted VQPs (MVQs) interacted with specific sub-groups of WRKY transcription factors in a VQ-motif-dependent manner. In some cases, the MAPK appears to phosphorylate either the MVQ or the WRKY, while in other cases, both proteins have been reported to act as MAPK substrates. We propose a network of dynamic interactions between members from the MAPK, MVQ and WRKY families – either as binary or as tripartite interactions. The compositions of the WRKY-MVQ transcriptional protein complexes may change – for instance, through MPK3/6-mediated modulation of protein stability – and therefore control defense gene transcription.

Two new fungal pigments named schweinitzins A and B (1-2), together with (S)-torosachrysone-8-O-methyl ether (3) and emodin-6,8-di-O-methyl ether (4) have been isolated from the methanolic extract of the fruit bodies of Xylaria schweinitzii (Xylariaceae) collected in Cuc Phuong national park, Ninh Binh province, Vietnam, by silica gel column chromatography and preparative HPLC. Their structures were elucidated by spectroscopic analysis such as IR, UV-Vis, 2D NMR and FT-ICR-MS. In addition, two compounds (1 and 3) showed strong cytotoxicity against all four cancer cell lines, KB (a human epidermal carcinoma), MCF7 (human breast carcinoma), SK-LU-1 (human lung carcinoma) and HepG2 (hepatocellular carcinoma).

The essential oil from the leaves of Tagetes minuta L., growing wild in Yemen, was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. A total of 28 compounds were identified representing 74.2% of total oil composition. Major components of the essential oil were (Z)-ocimenone (15.9%), (E)-ocimenone (34.8%), (Z)-β-ocimene (8.3%), limonene (2.3%), (Z)-tagetone (1.8%), dihydrotagetone (1.4%) and an unidentified dimethylvinylketone derivative (20.6%). The oil showed moderate cytotoxic activity against MCF-7 breast tumor cells, with an IC50 of 54.7 ± 6.2 μg/mL. In the DPPH radical scavenging assay, T. minuta oil showed potent antiradical activity with an IC50 value of 36 μg/mL. Antimicrobial activity was also investigated on several microorganisms, and the essential oil exhibited high activity against methicillin-resistant Staphylococcus aureus (MRSA) with an inhibition zone of 23 mm. It also exhibited remarkable antifungal activity against Candida albicans with an inhibition zone of 26 mm.