Drought resistance of Sorghum bicolor. 6. Changes in endogenous growth regulators of plants grown across an irrigation gradient

A gradient of water stress was created among sorghum plants with a line-source sprinkler irrigation system. Changes in endogenous growth regulators, leaf water potential (ψw), solute potential (ψs), leaf conductance, leaf temperature, leaf senescence, leaf area and plant height were monitored. Abscisic acid (AbA) levels were increased and phaseic acid (PA) levels were reduced under stress. IAA levels could not be related to stress. Leaf ψw, leaf ψs and leaf conductance were reduced and leaf temperature was increased by water stress. Leaf area development was more sensitive to stress than stem elongation. Linear correlations between irrigation, AbA, leaf ψw, leaf ψs and plant height were high (r > 0.9). The correlation between AbA and grain yield (r = − 0.65) was similar to that between irrigation and grain yield (r = 0.68), but opposite in sign. Leaf AbA content measured during early growth could thus be used to predict grain yield under a given irrigation regime.Key words: Abscisic acid, phaseic acid, indole-3-acetic acid, water stress, grain yield, sorghu

Heterologous production of the widely used natural food colorant carminic acid in <i>Aspergillus nidulans</i>

Abstract The natural red food colorants carmine (E120) and carminic acid are currently produced from scale insects. The access to raw material is limited and current production is sensitive to fluctuation in weather conditions. A cheaper and more stable supply is therefore desirable. Here we present the first proof-of-concept of heterologous microbial production of carminic acid in Aspergillus nidulans by developing a semi-natural biosynthetic pathway. Formation of the tricyclic core of carminic acid is achieved via a two-step process wherein a plant type III polyketide synthase (PKS) forms a non-reduced linear octaketide, which subsequently is folded into the desired flavokermesic acid anthrone (FKA) structure by a cyclase and a aromatase from a bacterial type II PKS system. The formed FKA is oxidized to flavokermesic acid and kermesic acid, catalyzed by endogenous A. nidulans monooxygenases, and further converted to dcII and carminic acid by the Dactylopius coccus C-glucosyltransferase DcUGT2. The establishment of a functional biosynthetic carminic acid pathway in A. nidulans serves as an important step towards industrial-scale production of carminic acid via liquid-state fermentation using a microbial cell factory

Characterization of a membrane-bound C-glucosyltransferase responsible for carminic acid biosynthesis in Dactylopius coccus Costa

Carminic acid is a widely applied red colorant that is still harvested from insects because its biosynthesis is not fully understood. Here, the authors identify and characterize a membrane-bound C-glucosyltransferase catalyzing the final step during carminic acid biosynthesis

Contrasting Roles for TLR Ligands in HIV-1 Pathogenesis

The first line of a host's response to various pathogens is triggered by their engagement of cellular pattern recognition receptors (PRRs). Binding of microbial ligands to these receptors leads to the induction of a variety of cellular factors that alter intracellular and extracellular environment and interfere directly or indirectly with the life cycle of the triggering pathogen. Such changes may also affect any coinfecting microbe. Using ligands to Toll-like receptors (TLRs) 5 and 9, we examined their effect on human immunodeficiency virus (HIV)-1 replication in lymphoid tissue ex vivo. We found marked differences in the outcomes of such treatment. While flagellin (TLR5 agonist) treatment enhanced replication of CC chemokine receptor 5 (CCR 5)-tropic and CXC chemokine receptor 4 (CXCR4)-tropic HIV-1, treatment with oligodeoxynucleotide (ODN) M362 (TLR9 agonist) suppressed both viral variants. The differential effects of these TLR ligands on HIV-1 replication correlated with changes in production of CC chemokines CCL3, CCL4, CCL5, and of CXC chemokines CXCL10, and CXCL12 in the ligand-treated HIV-1-infected tissues. The nature and/or magnitude of these changes were dependent on the ligand as well as on the HIV-1 viral strain. Moreover, the tested ligands differed in their ability to induce cellular activation as evaluated by the expression of the cluster of differentiation markers (CD) 25, CD38, CD39, CD69, CD154, and human leukocyte antigen D related (HLA)-DR as well as of a cell proliferation marker, Ki67, and of CCR5. No significant effect of the ligand treatment was observed on apoptosis and cell death/loss in the treated lymphoid tissue ex vivo. Our results suggest that binding of microbial ligands to TLRs is one of the mechanisms that mediate interactions between coinfected microbes and HIV-1 in human tissues. Thus, the engagement of appropriate TLRs by microbial molecules or their mimetic might become a new strategy for HIV therapy or prevention

SHINE Transcription Factors Act Redundantly to Pattern the Archetypal Surface of Arabidopsis Flower Organs

Floral organs display tremendous variation in their exterior that is essential for organogenesis and the interaction with the environment. This diversity in surface characteristics is largely dependent on the composition and structure of their coating cuticular layer. To date, mechanisms of flower organ initiation and identity have been studied extensively, while little is known regarding the regulation of flower organs surface formation, cuticle composition, and its developmental significance. Using a synthetic microRNA approach to simultaneously silence the three SHINE (SHN) clade members, we revealed that these transcription factors act redundantly to shape the surface and morphology of Arabidopsis flowers. It appears that SHNs regulate floral organs' epidermal cell elongation and decoration with nanoridges, particularly in petals. Reduced activity of SHN transcription factors results in floral organs' fusion and earlier abscission that is accompanied by a decrease in cutin load and modified cell wall properties. SHN transcription factors possess target genes within four cutin- and suberin-associated protein families including, CYP86A cytochrome P450s, fatty acyl-CoA reductases, GSDL-motif lipases, and BODYGUARD1-like proteins. The results suggest that alongside controlling cuticular lipids metabolism, SHNs act to modify the epidermis cell wall through altering pectin metabolism and structural proteins. We also provide evidence that surface formation in petals and other floral organs during their growth and elongation or in abscission and dehiscence through SHNs is partially mediated by gibberellin and the DELLA signaling cascade. This study therefore demonstrates the need for a defined composition and structure of the cuticle and cell wall in order to form the archetypal features of floral organs surfaces and control their cell-to-cell separation processes. Furthermore, it will promote future investigation into the relation between the regulation of organ surface patterning and the broader control of flower development and biological functions

Regulation of abscisic acid concentration in leaves of field-grown pearl millet (Pennisetum americanum (L.) Leeke): the role of abscisic acid export

Diurnal changes in the ABA concn. in leaves of droughted, field-grown plants of P. americanum were not always correlated with changes in bulk leaf water potential. A rapid decline in ABA content of the leaves following its rise to a peak level in mid-morning, was observed in several time-course studies despite continued water stress. The possibility that the reduction in ABA in leaves was due to an elevated rate of its export was examined by measuring ABA concn. in developing panicles (possible sinks for leaf-produced ABA) and in leaves, and by comparing the amounts of ABA in ungirdled leaves and in leaves heat-girdled at the base of the lamina to block export. ABA concn. in panicles generally paralleled those in leaves, though the peak concn. of ABA in the morning in panicles occurred later than in the leaves in some samplings. Although girdling initially increased ABA concn., it did not prevent a subsequent fall which generally paralleled the decline observed in untreated leaves. The decrease in ABA that occurred despite the block to export and despite continuing stress was attributed to changes in the synthesis or metabolism of ABA within the leaf. The probable rate of export of ABA from leaves, calculated from the changes in its concn. due to girdling, was highest at the time of most rapid ABA accumulation and declined thereafter. The percentage export of recently assimilated C declined similarly. However, the probable absolute rate of export of photosynthate, computed from stomatal conductance and [14C]-export measurements, was not uniquely related to that of AB