Molecular characterization of the <Emphasis Type="Italic">Aspergillus fumigatus NCS-1</Emphasis> homologue,NcsA

Here, we characterize the Aspergillus fumigatus homologue ncsA Neuronal Calcium Sensor. We showed that ncsA is not an essential gene and ?ncsA growth was decreased in the presence of EGTA and SDS. Furthermore, the ?ncsA mutant is more resistant to calcium chloride. NcsA:mRFP localizes to the cytoplasm and its cellular localization is not affected by the cellular response to either calcium chloride or EGTA. The ?ncsA mutant strain is more sensitive to voriconazole, itraconazole, and amphotericin. Polar growth in the ΔncsA mutant was also considerably more affected by lovastatin than in the wild type strain. The Spitzenkörper can be visualized in both strains and although the vacuolar system does not seem to be very different, there is an increase in the staining intensity on the germling surface of the ?ncsA strain. NcsA promotes pmcA and pmcB expression and therefore there is a reduced expression of these ion pumps in the ΔncsA mutant background, and also of other genes involved in the response to calcium in A. fumigatus. The ncsA inactivation mutation is not causing loss of virulence in a low dose murine infection when compared to the corresponding wild type strain.     

Genome-wide analysis and characterization of molecular evolution of the <Emphasis Type="Italic">HCT</Emphasis> gene family in pear (<Emphasis Type="Italic">Pyrus bretschneideri</Emphasis>)

Lignin is a major component of stone cells in pear fruit, which significantly affects fruit quality. Hydroxycinnamoyl CoA: shikimate hydroxycinnamoyl transferase (HCT), a recently discovered enzyme in plants, is an important gene that participates in the formation of lignin. Although HCT gene cloning and expression patterns have been studied in several species, including pear, there is still no extensive genome-wide bioinformatics analysis on the whole gene family, and the evolutionary history of HCT gene family is still unknown. A total of 82 HCT genes were identified in pear, most of which have one or two exons, and all with the conserved HXXXD motif and transferase domains. Based on the structural characteristics and phylogenetic analysis of these sequences, the HCT gene family genes could be classified into four main groups. Structural analysis also revealed that 25 % of HCT genes share a MYB binding site. Expansion of the HCT gene family mostly occurred before the divergence between Arabidopsis and Rosaceae, with whole-genome duplication or segmental duplication events playing the most important role in the expansion of the HCT gene family in pear. At the same time, purifying selection also played a critical role in the evolution of HCT genes. Five of the 82 HCT genes were verified by qRT-PCR to correspond to the pattern of stone cell formation during pear fruit development. The genome-wide identification, chromosome localization, gene structures, synteny, and expression analyses of pear HCT genes provide an overall insight into HCT gene family and their potential involvement in growth and development of stone cells.     

Overexpression of a <Emphasis Type="Italic">Miscanthus sacchariflorus</Emphasis> yellow stripe-like transporter <Emphasis Type="Italic">MsYSL1</Emphasis> enhances resistance of <Emphasis Type="Italic">Arabidopsis</Emphasis> to cadmium by mediating metal ion reallocation

The yellow stripe-like (YSL) family of transporters mediates the uptake, translocation, and distribution of various mineral elements in vivo by transferring metal ions chelated with phytosiderophore or nicotianamine (NA). However, little is known about the roles of the YSL genes against cadmium in planta. In this study, we first cloned and characterized a vital member of the YSL gene family, MsYSL1, from the bioenergy plant Miscanthus sacchariflorus. MsYSL1 localized in the plasma membrane and was widely expressed throughout the whole seedling with the highest expression level in the stem. In addition, its expression in the root was stimulated by excess manganese (Mn), cadmium (Cd), and lead, and a shortage of iron (Fe), zinc (Zn), and copper. Functional complementation in yeast indicated that MsYSL1 showed transport activity for Fe(II)–NA and Zn–NA, but not for Cd–NA. Although they exhibited no significant differences versus the wild type under normal cultivation conditions, MsYSL1-overexpressing Arabidopsis lines displayed a higher resistance to Cd accompanied by longer root lengths, lower Cd, Zn, and Mn levels in roots, and higher Cd, Fe, and Mn translocation ratios under Cd stress. Moreover, genes related to NA synthesis, metal translocation, long-distance transport, and Cd exclusion were highly induced in transgenic lines under Cd stress. Thus, MsYSL1 may be an essential transporter for diverse metal–NAs to participate in the Cd detoxification by mediating the reallocation of other metal ions.     

PbGLR3.3 Regulates Pollen Tube Growth in the Mediation of Ca<Superscript>2+</Superscript> Influx in <Emphasis Type="Italic">Pyrus bretschneideri</Emphasis>

Glutamate receptors (GluRs) are sensors of extracellular signals; they play important roles in the regulation of multiple physiological and developmental processes in eukaryotes. However, their functional roles in fruit trees are largely unknown. Here, based on the pear genome database, which was established in this lab, we identified 34 PbGLRs in pear (Pyrus bretschneideri Rehd), and they were divided into four groups by phylogenetic analysis. In comparisons with other groups, phylogenetic analyses and structural information of the PbGLRs in group 3 suggest that these genes underlie specific characteristics. Among the ten genes in group 3, we observed that the expression of PbGLR3.3 increased gradually during pollen germination and continuous growth, indicating that this gene might play a vital role in the development of pear pollen tubes. Using a combination of antisense oligodeoxy nucleotides and Ca²⁺-sensitive fluorescent probe methods, we verified that PbGLR3.3 participates in DSer-elicited intracellular Ca²⁺ signaling and Ca²⁺ regulation of growth in pear pollen tubes.     

Characterization and Expression Pattern of a Putative Pectin Methylesterase Gene, <Emphasis Type="Italic">BcMF27</Emphasis>, in <Emphasis Type="Italic">Brassica campestris</Emphasis> ssp. <Emphasis Type="Italic">chinensis</Emphasis>

Pectin methylesterases (PMEs) play an important role in modifying cell wall. PMEs catalyze the de-esterification of pectin, an important compound of cell wall, to affect fertility in plant reproduction. However, little especially molecular mechanism about pectin methylesterase is studied in recent years despite its importance to reproductive development in flower plant. Here the bioinformatics analysis of BcMF27 (Brassica campestris Male Fertility 27) (BRAD: Bra000541 GenBank: KT600012) sequence isolated from Brassica campestris L. ssp. chinensis showed its highly and characteristically conserved structure as a pectin methylesterase. Transient expression analysis in the onion epidermal cells revealed the product of BcMF27 was a transmembrane protein. Real-time RT-PCR and in situ hybridization suggested that BcMF27 was expressed in pollen grain and pollen tube. This study demonstrates that BcMF27 encodes a transmembrane pollen- and pollen tube-specific PME gene, and is also considered to help further understand the biological function of pectin methylesterases and the molecular mechanism of pollen development, pollen tube growth as a genic tool.     

<Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> calmodulin-like protein CML24 regulates pollen tube growth by modulating the actin cytoskeleton and controlling the cytosolic Ca<Superscript>2+</Superscript> concentration

Cytosolic free calcium ([Ca²⁺]_cyt), which is essential during pollen germination and pollen tube growth, can be sensed by calmodulin-like proteins (CMLs). The Arabidopsis thaliana genome encodes over 50 CMLs, the physiological role(s) of most of which are unknown. Here we show that the gene AtCML24 acts as a regulator of pollen germination and pollen tube extension, since the pollen produced by loss-of-function mutants germinated less rapidly than that of wild-type (WT) plants, the rate of pollen tube extension was slower, and the final length of the pollen tube was shorter. The [Ca²⁺]_cyt within germinated pollen and extending pollen tubes produced by the cml24 mutant were higher than their equivalents in WT plants, and pollen tube extension was less sensitive to changes in external [K⁺] and [Ca²⁺]. The pollen and pollen tubes produced by cml24 mutants were characterized by a disorganized actin cytoskeleton and lowered sensitivity to the action of latrunculin B. The observations support an interaction between CML24 and [Ca²⁺]_cyt and an involvement of CML24 in actin organization, thereby affecting pollen germination and pollen tube elongation.     

Deletion of <Emphasis Type="Italic">ldh</Emphasis>A and <Emphasis Type="Italic">ald</Emphasis>H genes in <Emphasis Type="Italic">Klebsiella</Emphasis><Emphasis Type="Italic">pneumoniae</Emphasis> to enhance 1,3-propanediol production

Objectives

To improve 1,3-propanediol (1,3-PD) production and reduce byproduct concentration during the fermentation of Klebsiella pneumonia.

Results

Klebsiella. pneumonia 2-1ΔldhA, K. pneumonia 2-1ΔaldH and K. pneumonia 2-1ΔldhAΔaldH mutant strains were obtained through deletion of the ldhA gene encoding lactate dehydrogenase required for lactate synthesis and the aldH gene encoding acetaldehyde dehydrogenase involved in the synthesis of ethanol. After fed-batch fermentation, the production of 1,3-PD from glycerol was enhanced and the concentrations of byproducts were reduced compared with the original strain K. pneumonia 2-1. The maximum yields of 1,3-PD were 85.7, 82.5 and 87.5 g/l in the respective mutant strains.

Conclusion

Deletion of either aldH or ldhA promoted 1,3-PD production in K. pneumonia.

     

Manifestation and inheritance of <Emphasis Type="Italic">tpd1</Emphasis> phenotype in the tobacco insertion mutant with extended flowering period

The tpd1 (from tobacco pollen development 1) insertion mutant of tobacco (Nicotiana tabacum L., cv. Samsun) with extended flowering period was investigated in detail in the course of plant development, and the inheritance of the mutant phenotype was established. The wild-type and mutant plants did not differ in basic developmental indices until the floral transition; later they diverged in the characteristics of male reproductive organs, particularly in anther development and pollen maturation. The pollen of tpd1 plants was underdeveloped and sterile, resulting in a characteristic seedless phenotype with extended flowering period. When mutant flowers were pollinated with wild-type pollen, the tpd1 phenotype was maintained in at least two seed generations, indicating that this trait was heritable. The tpd1 phenotype was closely linked with kanamycin resistance; it follows that the developmental anomalies observed in our experiments immediately depended on the vector DNA insert. Our data presume that tpd1 is a rare dominant monogenic mutation with a narrowly directed physiological manifestation. A model is presented to describe the effect of TPD1. The tpd1 mutant would help identify and clone the new TPD1 gene crucial for viable pollen development.     

ClpXP affects the cell metabolism of <Emphasis Type="Italic">Salmonella typhimurium</Emphasis> partially in an RpoS-dependent manner

Introduction

ClpXP protease is an important proteolytic system in Salmonella enterica serovar typhimurium (S. typhimurium). Inactivation of ClpXP by deletion of clpP resulted in overproduction of RpoS and a growth defect phenotype. Only one report has indicated that deleting rpoS can restore the growth of a S. typhimurium clpP mutant to the wild-type level. Whether overproduction of RpoS is responsible for the growth deficiency resulting from clpP disruption and how ClpXP affects the cell metabolism of S. typhimurium remain to be elucidated.

Objectives

The aim of this study is to investigate the effect of ClpXP on cell metabolism of S. typhimurium and explore the possible co-effect of RpoS associated with ClpXP in cell metabolism.

Method

We constructed a clpP rpoS double deletion mutant TT-19 (ΔclpP ΔrpoS TT-1) using a two-step phage transduction technique. We then compared the metabolite fingerprints of Salmonella rpoS deletion mutant TT-14 (ΔrpoS TT-1), clpP deletion mutant TT-16 (ΔclpP TT-1), and clpP rpoS double deletion mutant TT-19 (ΔclpP ΔrpoS TT-1) with those of the wild-type strain TT-1 by using gas chromatography coupled with mass spectrometry (GC–MS).

Results

Deletion of rpoS recovered only a part of the growth of Salmonella clpP mutant. Further metabolome analysis indicated that clpP disruption changed the levels of 16 extra- and 19 intracellular substances, while the extracellular concentrations of 4 compounds (serine, l-5-oxoproline, l-glutamic acid, and l-tryptophan) and intracellular concentrations of 10 compounds (l-isoleucine, glycine, serine, l-methionine, l-phenylalanine, malic acid, citric acid, urea, putrescine, and 6-hydroxypurine) returned to their wild-type levels when rpoS was also deleted.

Conclusion

ClpXP affects the cell metabolism of S. typhimurium partially in an RpoS-dependent manner.

     

The unusual gynoecium structure and extragynoecial pollen-tube pathway in <Emphasis Type="Italic">Phytolacca</Emphasis> (Phytolaccaceae)

The fusion of carpels into a unified compound gynoecium is considered a dominant feature of angiosperm evolution and it also occurs by postgenital fusion during the gynoecium development in some apocarpous species. However, we found the reverse process, the separation of carpels from combined carpel primordia, during the development of the gynoecium in Phytolacca. Semithin sectioning and scanning electron microscopy were utilised to observe the structure and development of the gynoecia in Phytolacca acinosa and Phytolacca americana, fluorescence microscopy was utilised to observe the pollen tube growth in the gynoecia of the two species, and the topology method was applied to analyze the relationship between the gynoecium structure and pollen tube pathway. Although the gynoecia of P. acinosa and P. americana are both syncarpous, the degree of carpel fusion in the mature gynoecia of the two syncarpous species is different as a result of variant developmental processes. However, change in the degree of carpel fusion during the development of gynoecia in Phytolacca does not affect pollen tube growth because of the existence of the extragynoecial pollen-tube pathway. Thus, the change in the degree of carpel fusion in Phytolacca is primarily the result of diversification of developmental processes related to selection pressure.     

Knockout of <Emphasis Type="Italic">OsACOS12</Emphasis> caused male sterility in rice

Pollen development in flowering plants is critical for male reproductive success. The pollen wall that protects the pollen from various environment stresses and bacterial infections plays an essential role in pollen development. The formation of pollen wall is associated with the biosynthesis and transport of sporopollenin components. ACOS5 in Arabidopsis encodes an acyl-CoA synthetase 5 required for sporopollenin biosynthesis. We identified the rice homolog of ACOS5 as OsACOS12. The CRISPR/Cas9-mediated OsACOS12 knockout mutant has complete male sterility due to a defect in pollen wall formation. β-Glucuronidase reporter gene analysis and RNA in situ hybridization indicated that OsACOS12 was specifically expressed in tapetum and microspores. The subcellular localization of OsACOS12-YFP demonstrated that OsACOS12 protein was primarily localized in the endoplasmic reticulum and nucleus. Our results suggest that OsACOS12 plays a critical and conserved role in pollen wall formation and pollen development and has implications in rice breeding.     

Cloning and Functional Analysis of <Emphasis Type="Italic">SaCLCc1</Emphasis>, a Gene Belonging to the Chloride Channel Family (<Emphasis Type="Italic">CLC</Emphasis>), from the Halophyte <Emphasis Type="Italic">Suaeda altissima</Emphasis> (L.) Pall.

One of the genes of the CLC (Chloride Channel) family, SaCLCc1, from the halophyte Suaeda altissima (L.) Pall. was cloned. To investigate the function of SaCLCc1, it was expressed in the S. cerevisiae deletion mutant Δgef1::LEU2 for the only gene of the CLC family in this organism. The growth of the transformed SaCLCc1-expressing mutant Δgef1 was restored when cells were grown in Fe²⁺-deficient YPEG medium, in minimal synthetic media SD and SR (pH 7.0), and in rich YPD medium containing Mn²⁺. The complementation of the Δgef1 mutant phenotype with the SaClCc1 gene indicates the involvement of the SaClCc1 protein in the transport of Cl^– ions.     

A novel dominant rice male sterility mutant, <Emphasis Type="Italic">OsDMS-1</Emphasis>, simultaneously controlled by independent loci on chromosomes 1, 2, and 3

We found a rice dominant genetic male-sterile mutant OsDMS-1 from tissue culture-regenerated offspring of Zhonghua 11 (japonica rice). Compared to Zhonghua 11, OsDMS-1 mutant anthers were narrow and pale and incapable of pollen release although the glume opened normally. Approximately 81.4% of this mutant pollen was small and malformed and could not be stained by iodine treatment. A paraffin section assay showed delayed degradation of the OsDMS-1 mutant tapetum without starch accumulation in the mutant pollen, ultimately leading to pollen abortion. Classical genetic analysis indicated that only one dominant gene controlled the sterility in the OsDMS-1 mutant. However, molecular mapping suggested three loci simultaneously control male sterility in this mutant: OsDMS-1A (on chromosome 1), flanked by InDel markers C1D4 and C1D5, OsDMS-1B (on chromosome 2), flanked by InDel markers C2D3 and C2D10, and OsDMS-1C (on chromosome 3), flanked by InDel markers 0315 and C3D3. Molecular mapping disagreed with classical genetic analysis regarding the number of genes controlling the OsDMS-1 mutant, indicating a novel mechanism underlying sterility in OsDMS-1. We present two hypotheses to explain this novel inheritance behavior: one is described as Parent-Originated Loci Tying Inheritance (POLTI); while the alternate hypothesis is described as Loci Recombination Lethal (LRL).     

In vitro inhibition of incompatible pollen tubes in <Emphasis Type="Italic">Nicotiana alata</Emphasis> involves the uncoupling of the F-actin cytoskeleton and the endomembrane trafficking system

In the S-RNase-based self-incompatibility system, subcellular events occurring in the apical region of incompatible pollen tubes during the pollen rejection process are poorly understood. F-actin dynamics and endomembrane trafficking are crucial for polar growth, which is temporally and spatially controlled in the tip region of pollen tubes. Thus, we developed a simple in vitro assay to study the changes in the F-actin cytoskeleton and the endomembrane system at the apical region of incompatible pollen tubes in Nicotiana alata. Growth but not germination of pollen tubes of S _c10 -, S ₇₀ -, and S ₇₅ -haplotypes was selectively inhibited by style extracts carrying the same haplotypes. Pollen F-actin cytoskeleton and endomembrane system, visualized by fluorescent markers, were normal during the initial 60 min of pollen culture in the presence of compatible and incompatible style extracts. Additional culture resulted in complete growth arrest and critical alterations in the integrity of the F-actin cytoskeleton and the endomembrane system of incompatible pollen tubes. The F-actin ring and the V-shaped zone disappeared from the apical region, while distorted F-actin cables and progressive formation of membrane aggregates evolved in the subapical region and the shank. The vacuolar network of incompatible pollen tubes invaded the tip region, but vacuolar membrane integrity remained mostly unaffected. The polar growth machinery of incompatible pollen tubes was uncoupled, as evidenced by the severe disruption of colocalization between the F-actin cytoskeleton and the endomembrane compartments. A model of pollen rejection integrating the main subcellular events occurring in incompatible pollen is discussed.     

Genetic complementation analysis of rice sucrose transporter genes in Arabidopsis <Emphasis Type="Italic">SUC2</Emphasis> mutant <Emphasis Type="Italic">atsuc2</Emphasis>

Sucrose transporters (SUTs) play a critical role on the phloem plasma membrane in loading sucrose into the phloem of source leaves for long-distance transport to sink organs. Rice has a small gene family of five SUTs, Oryza sativa SUT1 (OsSUT1) to OsSUT5. To identify rice SUTs that function as phloem loaders, we adopted a growth restoration assay of the severe growth retardation phenotype of atsuc2, a mutant of the best-characterized Arabidopsis phloem loader AtSUC2, by introducing OsSUTs. The rice SUT genes were expressed by two different promoters, the native phloem-specific promoter of AtSUC2 (pAtSUC2) and the constitutive Cauliflower Mosaic Virus 35S (pCaMV35S) promoter. Of all the transgenic atsuc2 plants, only pAtSUC2: OsSUT1 complemented the atsuc2 mutant phenotype in a comparable manner to wild type (WT), and consistent levels of soluble sugars and starch were recovered compared to those of WT. This suggests that OsSUT1 is a functional ortholog of the Arabidopsis AtSUC2 and functions as an apoplastic phloem loader. In addition, ossut1 mutants were produced via anther culture and their primary carbohydrate levels and growth phenotypes were indistinguishable from those of WT. This suggests that the rice phloem loader OsSUT1 function may not be essential for rice vegetative growth under normal conditions.     

Contribution of EmrAB efflux pumps to colistin resistance in <Emphasis Type="Italic">Acinetobacter baumannii</Emphasis>

Efflux pumps play an important role in antimicrobial resistance for Acinetobacter baumannii. However, the function of the Emr pump system and the relationship between Emr and drug resistance has not been characterized in A. baumannii. In this study, four possible groups of emr-like genes were found by searching a genome database. Among them, A1S_1772 (emrB) and A1S_1773 (emrA) were demonstrated to be co-transcribed as a single operon. Moreover, during osmotic stress, A1S_1772 showed the largest change in gene expression compared to the other emrB-like genes, and deletion of A1S_1772 (AB ΔemrB) significantly slowed cell growth in 20% sucrose. Using a phenotypic microarray analysis, the AB ΔemrB mutant was more susceptible to colistin and nafcillin, paromomycin, spiramycin, and D,L-serine hydroxmate than the wild type. The spot assay, time kill assay and minimal inhibition concentration determination also indicated that the wild type could tolerate colistin better than the AB ΔemrB mutant. Finally, the increased expression levels of all emrB-like genes, including A1S_0775, A1S_0909, A1S_1772, and A1S_1799, in colistin resistance-induced A. baumannii further supported the possible involvement of the emrB genes in A. baumannii colistin resistance. Together, the Emr pump systems in A. baumannii contribute to adaptation to osmotic stress and resistance to colistin.