Sex biased expression of hormone related genes at early stage of sex differentiation in papaya flowers

Sex types of papaya are controlled by a pair of nascent sex chromosomes,but molecular genetic mechanisms of sex determination and sex differentiation in papaya are still unclear.We performed comparative analysis of transcriptomic profiles of male and female floral buds at the early development stage before the initiation of reproductive organ primordia at which there is no morphological difference between male and female flowers.A total of 1734 differentially expressed genes(DEGs)were identified,of which 923 showed female-biased expression and 811 showed male-biased expression.Functional annotation revealed that genes related to plant hormone biosynthesis and signaling pathways,especially in abscisic acid and auxin pathways,were overrepresented in the DEGs.Transcription factor binding motifs,such as MYB2,GAMYB,and AP2/EREBP,were enriched in the promoters of the hormone-related DEGs,and transcription factors with those motifs also exhibited differential expression between sex types.Among these DEGs,we also identified 11 genes in the non-recombining region of the papaya sex chromosomes and 9 genes involved in stamen and carpel development.Our results suggested that sex differentiation in papaya may be regulated by multiple layers of regulation and coordination and involved transcriptional,epigenetic,and phytohormone regulation.Hormones,especially ABA and auxin,transcription factors,and genes in the non-recombination region of the sex chromosome could be involved in this process.Our findings may facilitate the elucidation of signal transduction and gene interaction in sex differentiation of unisexual flowers in papaya.

Factors involved in the success of Castanea henryi stem cuttings in different cutting mediums and cutting selection periods

Chinquapin(Castanea henryi) is a dual-purpose tree species in China valued for as a source of timber and starch.We investigated the effect of four cutting mediums(pure vermiculite;peat:river sand at 3:1 v/v;peat:krasnozem at 1:1 v/v;and pure krasnozem) and three stem cutting periods(March,May,and July) on rooting performance of C.henryi cuttings.Different cutting periods and cutting mediums greatly influenced the rooting rate of C.henryi,ranging from 3.35 to 77.31%.Principal component analysis indicated that the best combination of cutting period and cutting medium was semi-hardwood cuttings(May cuttings)+krasnozem.Histological evidence indicated that adventitious root initials were present by week 5-6,and that the site of root primordia initiation was observed in the vascular cambium.Stem anatomical structures observed at different periods indicated that a xylem/radius ratio of29.90-37.42% and a fractured phloem fiber ring are indicative of rooting success.The relational model between rooting index and medium properties indicated that nutrient content and porosity significantly influenced callus production.However,pH strongly affected C.henryi root formation,with the Pearson correlation coefficients for May and July cuttings of-0.856 and-0.947,respectively.Our protocol is helpful to achieve mass clone propagation of improved C.henryi genotypes,thus overcoming a common hurdle in chinquapin breeding programs.

PBS3 Protects EDS1 from Proteasome-Mediated Degradation in Plant Immunity

Plant immunity is controlled by both positive regulators such as PBS3 and EDS1 and negative regulators such as NPR3 and NPR4.However,the relationships among these important immune regulators remain elusive.In this study,we found that PBS3 interacts with EDS1 in both the cytoplasm and the nucleus,and is required for EDS1 protein accumulation?NPR3 and NPR4,which function as salicylic acid receptors and adaptors of Cullin3-based E3 ligase,interact with and mediate the degradation of EDS1 via the 26S proteasome.We further discovered that PBS3 inhibits the polyubiquitination and subsequent degradation of EDS1 by reducing the association of EDS1 with the Cullin3 adaptors NPR3 and NPR4.Furthermore,we showed that PBS3 and EDS1 also contribute to PAMP-triggered immunity in addition to effector-triggered immunity.Collectively,our study reveals a novel mechanism by which plants fine-tune defense resporises by inhibiting the degradation of a positive player in plant immunity.

Coordinated regulation of plant immunity by poly(ADP-ribosyl)ation and K63-linked ubiquitination

Poly(ADP-ribosyl)ation(PARylation)is a posttranslational modification reversibly catalyzed by poly(ADP-ribose)polymerases(PARPs)and poly(ADP-ribose)glycohydrolases(PARGs)and plays a key role in multi-ple cellular processes.The molecular mechanisms by which PARylation regulates innate immunity remain largely unknown in eukaryotes.Here we show that Arabidopsis UBC13A and UBC13B,the major drivers of lysine 63(K63)-linked polyubiquitination,directly interact with PARPs/PARGs.Activation of pathogen-associated molecular pattern(PAMP)-triggered immunity promotes these interactions and enhances PARylation of UBC13.Both parp1 parp2 and ubc13a ubc13b mutants are compromised in immune responses with increased accumulation of total pathogenesis-related(PR)proteins but decreased accu-mulation of secreted PR proteins.Protein disulfide-isomerases(PDIs),essential components of endo-plasmic reticulum quality control(ERQC)that ensure proper folding and maturation of proteins destined for secretion,complex with PARPs/PARGs and are PARylated upon PAMP perception.Significantly,PARylation of UBC13 regulates K63-linked ubiquitination of PDIs,which may further promote their disulfide isomerase activities for correct protein folding and subsequent secretion.Taken together,these results indicate that plant immunity is coordinately regulated by PARylation and K63-linked ubiquitination.

NLR immune receptor RB is differentially targeted by two homologous but functionally distinct effector proteins

Plant nucleotide-binding leucine-rich repeat(NLR)receptors mediate immune responses by directly or indirectly sensing pathogen-derived effectors.Despite significant advances in the understanding of NLR-mediated immunity,the mechanisms by which pathogens evolve to suppress NLR activation triggered by cognate effectors and gain virulence remain largely unknown.The agronomically important immune receptor RB recognizes the ubiquitous and highly conserved IPI-O RXLR family members(e.g.,IPI-O1)from Phytophthora infestans,and this process is suppressed by the rarely present and homologous effector IPIO4.Here,we report that self-association of RB via the coiled-coil(CC)domain is required for RB activation and is differentially affected by avirulence and virulence effectors.IPI-O1 moderately reduces the self-association of RB CC,potentially leading to changes in the conformation and equilibrium of RB,whereas IPIO4 dramatically impairs CC self-association to prevent RB activation.We also found that IPI-O1 associates with itself,whereas IPI-O4 does not.Notably,IPI-O4 interacts with IPI-O1 and disrupts its self-association,therefore probably blocking its avirulence function.Furthermore,IPI-O4 enhances the interaction between RB CC and IPI-O1,possibly sequestering RB and IPI-O1 and subsequently blocking their interactions with signaling components.Taken together,these findings considerably extend our understanding of the underlying mechanisms by which emerging virulent pathogens suppress the NLR-mediated recognition of cognate effectors.

Growth,nutritional quality,and energy use efficiency in two lettuce cultivars as influenced by white plus red versus red plus blue LEDs

Red plus blue light-emitting diodes(LEDs)are commonly applied in plant factories with artificial lighting due to photosynthetic pigments,which absorb strongly in red and blue light regions of the spectrum.However,plants grown under natural environment are used to utilizing broad-wide spectrum by long-term evolution.In order to examine the effects of addition light added in red plus blue LEDs or white LEDs,green and purple leaf lettuces(Lactuca sativa L.cv.Lvdie and Ziya)were hydroponically cultivated for 20 days under white LEDs,white plus red LEDs,red plus blue LEDs,and red plus blue LEDs supplemented with ultraviolet,green or far-red light,respectively.The results indicated that the addition of far-red light in red plus blue LEDs increased leaf fresh and dry weights of green leaf lettuce by 28%and 34%,respectively.Addition of ultraviolet light did not induce any differences in growth and energy use efficiency in both lettuce cultivars,while supplementing green light with red plus blue LEDs reduced the vitamin C content of green leaf lettuce by 44%and anthocyanin content of purple leaf lettuce by 30%compared with red plus blue LEDs,respectively.Spectral absorbencies of purple leaf lettuce grown under red plus blue LEDs supplemented with green light were lower in green light region compared with those grown under red plus blue LEDs,which was associated with anthocyanin contents.White plus red LEDs significantly increased leaf fresh and dry weights of purple leaf lettuce by 25%,and no significant differences were observed in vitamin C and nitrate contents compared with white LEDs.Fresh weight,light and electrical energy use efficiencies of hydroponic green and purple leaf lettuces grown under white plus red LEDs were higher or no significant differences compared with those grown under red plus blue LEDs.In conclusion,white plus red LEDs were suggested to substitute for red plus blue LEDs in hydroponic lettuce(cv.Lvdie and Ziya)production in plant factories with artificial lighting.