Genome-wide identification and characterization of ACBP gene family in Populus reveal salinity alkali-responsive profiles

Acyl-CoA-binding proteins(ACBPs)are important for the transport of acyl groups for macro molecular biosynthesis involved in plant growth,development,and diverse stress(e.g.,cold,drought,salinity,and heavy metals)responses.Here,we report the phylogeny and characteristics of the ACBP family in the woody plant Populus trichocarpa.Eight genes encoding ACBP proteins were identified,and they are distributed on eight chromosomes in P.trichocarpa.These PtACBP genes were divided into four subgroups according to gene structure,conserved motifs and phylogenetic relationship.Promoter analysis revealed that cis-elements were related to stress response,phytohormone response,and physical and reproductive growth regulation.Expression levels of PtACBP genes varied among different organs,with the highest expression in leaves and the lowest in stems.Quantitative real-time PCR(qRT-PCR)analysis showed that under salinity-alkali stresses(i.e.,200 mM NaCl,75 mM Na2CO3,and 100 mM NaHCO3),four(PtACBP1,PtACBP3,PtACBP4 and PtACBP8)of eight PtACBP genes were significantly induced in roots and leaves.These data provide a comprehensive analysis of the ACBPs family in P.trichocarpa,which could be useful for gene function analyses.

Selenium-enriched and ordinary green tea extracts prevent high blood pressure and alter gut microbiota composition of hypertensive rats caused by high-salt diet

High-salt diet is well recognized as a risk factor for hypertension,and dietary intervention plays a critical role in the prevention of hypertension.The current study investigated the effects of selenium-enriched green tea(Se-GT)and ordinary green tea(GT)on prevention of hypertension of rats induced by high-salt diet,as well as their potential regulatory and mechanism.Our results showed that GT and Se-GT supplementations significantly prevented the increase of blood pressure(BP),activated the phosphoinosmde-3-kinase/protein kinase B(PI3K/Akt)signaling pathway,and regulated the gene expression related to BP,as well as improved the tissue damage like heart,liver,and kidneys.Besides,the key parameters associated with oxidative stress,inflammation and endothelial dysfunction were also altered by GT and Se-GT treatments.Importantly,GT or Se-GT administration adjusted the diversity and composition of the intestinal flora.Moreover,GT and Se-GT supplementations increased the abundance of beneficial bacteria and reduced the abundance of harmful or conditional pathogenic bacteria.More specifically,GT intake specifically and significantly enriched the relative abundance of Paraprevotella and Bacteroides,whereas Se-GT was characterized by specific and significant enrichment for Allobaculum and Bifidobacterium.Our results proved that dietary supplement of GT and Se-GT remarkably improved the vascular functions and effectively prevented tissue damage by regulation of intestinal flora,and thus preventing hypertension induced by high-salt diet.

The contributions of sporophytic tapetum to pollen formation

Successful pollen formation is essential for plant reproduction.During anther development,microspore mother cells undergo meiosis to form tetrads.After being released from the tetrad,microspores develop into mature pollen.The tapetum is the innermost layer of anther somatic cells and forms a locule to provide nutrition,enzymes and pollen wall materials for microspore development.Based on the male sterile phenotype,many genes important for tapetum and pollen development have been cloned.In this review,we highlight the genetic pathway of DYT1-TDF1-AMS-MS188-MS1 which acts in tapetal development in Arabidopsis.We also compared this genetic pathway in different species such as Arabidopsis,rice and maize.Based on this pathway,we review recent findings and insights into the contribution of the tapetum to pollen formation at the molecular level.1)Tapetum provides nutrition for microspore development.2)Tapetum provides enzymes to dissolve pectin and callose to release microspores from tetrads.3)Tapetum synthesizes precursors for pollen wall formation via different molecular pathways.4)Tapetum provides precursors for pollen coat formation.5)Tapetum provides small RNAs to regulate genic methylation in the germline cells.

The regulatory mechanism of rapid lignification for timely anther dehiscence

Anther dehiscence is a crucial event in plant reproduction,tightly regulated and dependent on the lignification of the anther endothecium.In this study,we investigated the rapid lignification process that ensures timely anther dehiscence in Arabidopsis.Our findings reveal that endothecium lignification can be divided into two distinct phases.During Phase Ⅰ,lignin precursors are synthesized without polymerization,while Phase Ⅱ involves simultaneous synthesis of lignin precursors and polymerization.The transcription factors MYB26,NST1/2,and ARF17 specifically regulate the pathway responsible for the synthesis and polymerization of lignin monomers in Phase Ⅱ.MYB26-NST1/2 is the key regulatory pathway responsible for endothecium lignification,while ARF17 facilitates this process by interacting with MYB26.Interestingly,our results demonstrate that the lignification of the endothecium,which occurs within approximately 26 h,is much faster than that of the vascular tissue.These findings provide valuable insights into the regulation mechanism of rapid lignification in the endothecium,which enables timely anther dehiscence and successful pollen release during plant reproduction.

Exploring the diversity of plant proteome

The tremendous functional,spatial,and temporal diversity of the plant proteome is regulated by multiple factors that continuously modify protein abundance,modifications,interactions,localization,and activity to meet the dynamic needs of plants.Dissecting the proteome complexity and its underlying genetic variation is attracting increasing research attention.Mass spectrometry(MS)‐based proteomics has become a powerful approach in the global study of protein functions and their relation-ships on a systems level.Here,we review recent breakthroughs and strategies adopted to unravel the diversity of the proteome,with a specific focus on the methods used to analyze posttranslational modifications(PTMs),protein localization,and the organization of proteins into functional modules.We also consider PTM crosstalk and multiple PTMs temporally regulating the life cycle of proteins.Fi-nally,we discuss recent quantitative studies using MS to measure protein turnover rates and examine future directions in the study of the plant proteome.

The rice OsV4 encoding a novel pentatricopeptide repeat protein is required for chloroplast development during the early leaf stage under cold stress

Pentatricopeptide repeat （PPR） proteins, charac- terized by tandem arrays of a 35 amino acid motif, have been suggested to play central and broad roles in modulating the expression of organelle genes in plants. However, the molecular mechanisms of most rice PPR genes remains unclear. In this paper, we isolated and characterized a temperature-conditional virescent mutant, OsV4, in rice （Oryza sativa cultivar Jiahual （WT, japonica rice variety））. The mutant displays albino phenotype and abnormal chloroplasts at the three leaf stage, which gradually turns green after the four leaf stage at a low temperature （20℃）. But the mutant always develops green leaves and well-developed chloroplasts at a high temperature （32℃）. Genetic and molecular analyses uncovered that OsV4 encodes a novel chloroplast-targeted PPR protein including four PPR motifs. Further investigations show that the mutant phenotype is associated with changes in chlorophyll content and chloroplast development. The OsV4 transcripts only accumulate to high levels in young leaves, indicating that its expression is tissue-specific. In addition, transcript levels of some ribosomal components and plastid- encoded polymerase-dependent genes are dramatically re- duced in the albino mutants grown at 20℃. These findings suggest that OsV4 plays an important role during early chloroplast development under cold stress in rice.

Efficient generation of homozygous substitutions in rice in one generation utilizing an rABE8e base editor

A new deaminase,TadA8e,was recently evolved in the laboratory.TadA8e catalyzes DNA deamination over 1,000 times faster than ABE7.10.We developed a high-efficiency adenine base editor,rABE8e(rice ABE8e),combining monomeric TadA8e,bis-bpNLS and codon optimization.rABE8e had substantially increased editing efficiencies at NG-protospacer adjacent motif(PAM)and NGG-PAM target sequences compared with ABEmax.For most targets,rABE8e exhibited nearly 100%editing efficiency and high homozygous substitution rates in the specific editing window,especially at Positions A5 and A6.The ability to rapidly generate plant materials with homozygous base substitutions will benefit gene function research and precision molecular breeding.

A cellular mechanism underlying the restoration of thermo/photoperiod-sensitive genic male sterility

During anther development,the transformation of the microspore into mature pollen occurs under the pro-tection of first the tetrad wall and later the pollen wall.Mutations in genes involved in this wall transition often lead to microspore rupture and male sterility;some such mutants,such as the reversible male sterile(rvms)mutant,are thermo/photoperiod-sensitive genic male sterile(P/TGMS)lines.Previous studies have shown that slow development is a general mechanism of P/TGMS fertility restoration.In this study,we iden-tified restorer of rvms-2(res2),which is an allele of QUARTET3(QRT3)encoding a polygalacturonase that shows delayed degradation of the tetrad pectin wall.We found that MS188,a tapetum-specific transcrip-tion factor essential for pollen wall formation,can activate QRT3 expression for pectin wall degradation,indicating a non-cell-autonomous pathway involved in the regulation of the cell wall transition.Further as-says showed that a delay in degradation of the tetrad pectin wall is responsible for the fertility restoration of rvms and other P/TGMS lines,whereas early expression of QRT3 eliminates low temperature restoration of rvms-2 fertility.Taken together,these results suggest a likely cellular mechanism of fertility restoration in P/TGMS lines,that is,slow development during the cell wall transition of P/TGMS microspores may reduce the requirement for their wall protection and thus support their development into functional pollens,leading to restored fertility.

Promotion mechanism of self-transmissible degradative plasmid transfer in maize rhizosphere and its application in naphthalene degradation in soil

Rhizospheres can promote self-transmissible plasmid transfer,however,the corresponding mechanism has not received much attention.Plant-microbe remediation is an effective way to promote pollutant biodegradation;however,some pollutants,such as naphthalene,are harmful to plants and result in inefficient plant-microbe remediation.In this study,trans-fer of a TOL-like plasmid,a self-transmissible plasmid loaded with genetic determinants for pollutant degradation,among different bacteria was examined in bulk and rhizosphere soils as well as addition of maize root exudate and its artificial root exudate(ARE).The results showed that the numbers of transconjugants and recipients as well as bacterial metabolic activities,such as xylE mRNA expression levels and catechol 2,3-dioxygenase(C23O)activ-ities of bacteria,remained high in rhizosphere soils,when compared with bulk soils.The number of transconjugants and bacterial metabolic activities increased with the increasing exudate and ARE concentrations,whereas the populations of donor and recipient bacteria were substantially unaltered at all concentrations.All the experiments consistently showed that a certain number of bacteria is required for self-transmissible plasmid transfer,and that the increased plasmid transfer might predominantly be owing to bacterial metabolic activ-ity stimulated by root exudates and ARE.Furthermore,ARE addition increased naphthalene degradation by transconjugants in both culture medium and soil.Thus,the combined action of a wide variety of components in ARE might contribute to the increased plasmid transfer and naphthalene degradation.These findings suggest that ARE could be an effectively al-ternative for plant-microbe remediation of pollutants in environments where plants cannot survive.

Na_(2)CO_(3)-responsive Photosynthetic and ROS Scavenging Mechanisms in Chloroplasts of Alkaligrass Revealed by Phosphoproteomics

Alkali-salinity exerts severe osmotic,ionic,and high-p H stresses to plants.To understand the alkali-salinity responsive mechanisms underlying photosynthetic modulation and reactive oxygen species(ROS)homeostasis,physiological and diverse quantitative proteomics analyses of alkaligrass(Puccinellia tenuiflora)under Na_(2)CO_(3)stress were conducted.In addition,Western blot,real-time PCR,and transgenic techniques were applied to validate the proteomic results and test the functions of the Na_(2)CO_(3)-responsive proteins.A total of 104 and 102 Na_(2)CO_(3)-responsive proteins were identified in leaves and chloroplasts,respectively.In addition,84 Na_(2)CO_(3)-responsive phosphoproteins were identified,including 56 new phosphorylation sites in 56 phosphoproteins from chloroplasts,which are crucial for the regulation of photosynthesis,ion transport,signal transduction,and energy homeostasis.A full-length Pt FBA encoding an alkaligrass chloroplastic fructosebisphosphate aldolase(FBA)was overexpressed in wild-type cells of cyanobacterium Synechocystis sp.Strain PCC 6803,leading to enhanced Na_(2)CO_(3)tolerance.All these results indicate that thermal dissipation,state transition,cyclic electron transport,photorespiration,repair of photosystem(PS)Ⅱ,PSI activity,and ROS homeostasis were altered in response to Na_(2)CO_(3)stress,which help to improve our understanding of the Na_(2)CO_(3)-responsive mechanisms in halophytes.

The pentatricopeptide repeat protein EMB1270 interacts with CFM2 to splice specific group Ⅱ introns in Arabidopsis chloroplasts

Chloroplast biogenesis requires the coordinated expression of chloroplast and nuclear genes.Here, we show that EMB1270, a plastid-localized pentatricopeptide repeat(PPR) protein, is required for chloroplast biogenesis in Arabidopsis thaliana.Knockout of EMB1270 led to embryo arrest,whereas a mild knockdown mutant of EMB1270 displayed a virescent phenotype. Almost no photosynthetic proteins accumulated in the albino emb1270 knockout mutant. By contrast, in the emb1270 knockdown mutant, the levels of ClpP1 and photosystem I(PSI) subunits were significantly reduced, whereas the levels of photosystem II(PSII) subunits were normal. Furthermore, the splicing efficiencies of the clpP1.2,ycf3.1, ndhA, and ndhB plastid introns were dramatically reduced in both emb1270 mutants. RNA immunoprecipitation revealed that EMB1270 associated with these introns in vivo. In an RNA electrophoretic mobility shift assay(REMSA), a truncated EMB1270 protein containing the 11 Nterminal PPR motifs bound to the predicted sequences of the clpP1.2, ycf3.1, and ndhA introns.In addition, EMB1270 specifically interacted with CRM Family Member 2(CFM2). Given that CFM2 is known to be required for splicing the same plastid RNAs, our results suggest that EMB1270 associates with CFM2 to facilitate the splicing of specific group II introns in Arabidopsis.

Fern spore germination in response to environmental factors

Fern spore germination gives rise to the rhizoid and protonemal cell through asymmetric cell division, and then develops into a gametophyte. Spore germination is also a representative single-cell model for the investigation of nuclear polar movement, asymmetrical cell division, polarity establishment and rhizoid tip-growth. These processes are affected by various environmental factors, such as light, gravity, phytohormones, metal ions, and temperature. Here, we present a catalog of spore germination in response to different environmental factors. They are as follows： （1） Representative modes of light affecting spore germination from different fern species include red light-stimulated and far red light-inhibited spore germination, far red light-uninhibited spore germination, blue light-inhibited spore germination, and spore germination in the dark. The optimal light intensity and illumination time for spore germination are different among various fern species. Light response upon spore germination is initiated from the cell mitosis that regulated by phytochromes （PHYs） and cryptochromes （CRYs）. AcPHY2, AcCRY3 and/or AcCRY4 are hypothesized to be involved in spore germination; （2） Gravity and calcium are crucial to early nuclear movement and polarity establishment of spores; （3） Gibberellin and antheridiogen can initiate and promote spore germination in many species, but abscisic acid, jasmonic acid, and ethylene pose only minor effects; （4） Spores can obtain the maximal germination rate in their favorable growth medium. Moreover, metal ions, pH, and spore density in the culture medium also affect spore germination; （5） Most fern spores germinate at 25℃, and an optimal CO2 concentration is necessary for spore germination of certain fern plants. These provide valuable information for understanding fern spore germination in response to environmental factors.

Arabidopsis CAP1 mediates ammonium-regulated root hair growth by influencing vesicle trafficking and the cytoskeletal arrangement in root hair cells

Plant root hairs are essential for mineral and water absorption,which possess sophisticated sensory mechanisms to allow them to respond to different environmental signals.Ammonium(NH^(+))is a major form of nitrogen in the soil.NH^(+)can influence the root system architecture,such as root hair growth(Liu and von Wir en,2017).