MdGSTF6,activated by MdMYB1,plays an essential role in anthocyanin accumulation in apple

Anthocyanins are biosynthesized on the cytosolic surface of the endoplasmic reticulum and then transported into the vacuole for storage.Glutathione S-transferases(GSTs)are considered to be responsible for the transport of anthocyanins into the vacuole.However,the regulatory mechanisms of GSTs in plants are still unclear.Here,we performed a genome-wide analysis and identified 69 GST genes in apple.The expression of MdGSTF6 was positively correlated with the anthocyanin content(r=0.949)during‘Yanfu 8’fruit development.The overexpression of MdGSTF6 in the Arabidopsis thaliana tt19 mutant resulted in seedlings of 35S::MdGSTF6-GFP/tt19 that could accumulate anthocyanin and rescue its phenotype,suggesting that MdGSTF6 was an anthocyanin transporter.The silencing of MdGSTF6 affected anthocyanin accumulation in apple fruit.Moreover,the knockdown of MdGSTF6 by RNA interference in cultured‘Gala’seedlings inhibited anthocyanin accumulation.The interaction experiments showed that MdMYB1 could bind directly to the MdGSTF6 promoter to transcriptionally activate its expression.Collectively,our results demonstrate that MdGSTF6 encodes an important GST transporter of anthocyanins in apple fruit and provide evidence for the associated regulatory mechanisms.Therefore,MdMYB1 can not only regulate anthocyanin synthesis,but also control the transport of anthocyanin in apples.This information may be useful for further clarifying the regulation of anthocyanin transport in apple.

Extracellular and intracellular infection of Botryosphaeria dothidea and resistance mechanism in apple cells

Apple ring rot,which is caused by Botryosphaeria dothidea,severely affects apple production.The mechanisms employed in apple cells against B.dothidea remain unknown.In this research,the pathogen infection mode and the relationship between cell death and disease resistance in‘Fuji’/B.dothidea interaction pathosystem were investigated.By using transmission electron microscopy(TEM),our research showed that the pathogen infects apple cells both intracellularly and extracellularly.However,compared with that in immature fruit,the incidence of hyphae in the interior of mature apple fruit cells increased dramatically,suggesting that cell wall-mediated penetration resistance could be important in apple resistance against B.dothidea.TEM ultrastructural characterization identified the nuclear morphology of programmed cell death induction in both apple fruit and callus cells under B.dothidea infection.Overexpression of MdVDAC2(MDP0000271281),which encodes an outer-membrane localized anion channel protein in mitochondria,significantly promoted cell death under B.dothidea infection and simultaneously inhibited pathogen infection,suggesting that cell death represents a disease resistance mechanism in apple against B.dothidea infection.Furthermore,BdCatalase(KAF4307763),a cytochromeP450 family protein BdCYP52A4(KAF4300696),and subtilisin-domain containing proteinswere identified fromB.dothidea-secreted proteins,which suggested the potential involvement of active oxygen species and phytoalexins in combating B.dothidea infection and triggering or dampening apple resistance.Collectively,our research suggested that cell wall-mediated penetration resistance,programmed cell death machinery and microbial effector-interrelated signaling were among strategies recruited in apple to combat B.dothidea.The current research laid the foundation for further investigations into resistance mechanisms in apple.

Activation of disease resistance against Botryosphaeria dothidea by downregulating the expression of MdSYP121 in apple

In plants,the vesicle fusion process plays a vital role in pathogen defence.However,the importance of the vesicle fusion process in apple ring rot has not been studied.Here,we isolated and characterised the apple syntaxin gene MdSYP121.Silencing the MdSYP121 gene in transgenic apple calli increased tolerance to Botryosphaeria dothidea infection;this increased tolerance was correlated with salicylic acid(SA)synthesis-related and signalling-related gene transcription.In contrast,overexpressing MdSYP121 in apple calli resulted in the opposite phenotypes.In addition,the results of RNA sequencing(RNA-Seq)and quantitative real-time PCR(qRT-PCR)assays suggested that MdSYP121 plays an important role in responses to oxidation–reduction reactions.Silencing MdSYP121 in apple calli enhanced the expression levels of reactive oxygen species(ROS)-related genes and the activity of ROS-related enzymes.The enhanced defence response status in MdSYP121-RNAi lines suggests that syntaxins are involved in the defence response to B.dothidea.More importantly,we showed that MdSYP121 forms a soluble N-ethylmaleimide-sensitive factor attachment protein receptor(SNARE)complex with MdSNAP33,and the complex may participate in regulating resistance to B.dothidea.In conclusion,by regulating the interaction of SA pathway and oxidation–reduction process,MdSYP121 can influence the pathogen infection process in apple.

Development of potent promoters that drive the efficient expression of genes in apple protoplasts

Protoplast transient expression is a powerful strategy for gene functional characterization,especially in biochemical mechanism studies.We herein developed a highly efficient transient expression system for apple protoplasts.The abilities of the Arabidopsis thaliana and Malus domestica ubiquitin-10(AtUBQ10 and MdUBQ10)promoters to drive the expression of multiple genes were compared with that of the CaMV 35S promoter,and the results revealed that the AtUBQ10 and MdUBQ10 promoters were more efficient in apple protoplasts.With this system,we demonstrated that active AtMKK7ac could activate MAPK6/3/4 signaling cascades,which further regulated MdWRKY33 phosphorylation and stability in apple.Furthermore,the ligand-induced interaction between the immune receptor AtFLS2 and the coreceptor AtBAK1 was reconstituted in apple protoplasts.We also found that the stability of the bacterial effector AvrRpt2 was regulated by feedback involving auxin and the immune regulator RIN4.The system established herein will serve as a useful tool for the molecular and biochemical analyses of apple genes.

Recent Advances in Understanding Plant Heterosis

Although heterosis is widely utilized in crop production, its genetic and molecular basis is still elusive. It is arguably that heterosis arises in crosses between genetically and/or epigenetically distinct individuals. Various genetic models have been proposed to explain heterosis, such as dominance and overdominance hypothesis. With the recent advancements in functional genomics, epigenetics, transcriptomics, proteomics, and metabolomics-related technologies, systems-level approaches have been adopted to understand the molecular basis of heterosis. In this review, we gather a brief account of findings from various studies in order to better understand the genetic and molecular basis of heterosis.

Cucumber Downy Mildew: Research Progress and Registered Fungicides

Downy mildew is an important disease of cucumber,seriously threatening the production of cucumber.This article briefly described the symptoms and pathogen characteristics of cucumber downy mildew,the pathogenesis of the pathogen,plant disease resistance,pathogen drug resistance and integrated prevention and control techniques.In addition,officially registered fungicides,which are used against cucumber downy mildew,were summarized and categorized.We emphatically analyzed the active ingredients and formula combinations of the fungicides for controlling cucumber downy mildew,and the problems of the registered fungicides.The characteristics and control techniques of the newly registered fungicides for controlling cucumber downy mildew in the past two years are introduced.The problems existing in the research of cucumber downy mildew are discussed.Finally,the future research direction is put forward.

New definition of metabolic dysfunction-associated fatty liver disease with elevated brachial-ankle pulse wave velocity and albuminuria: a prospective cohort study

A new definition of metabolic dysfunction-associated fatty liver disease(MAFLD)has recently been proposed.We aim to examine the associations of MAFLD,particularly its discordance from non-alcoholic fatty liver disease(NAFLD),with the progression of elevated brachial-ankle pulse wave velocity(baPWV)and albuminuria in a community-based study sample in Shanghai,China.After 4.3 years of follow-up,778 participants developed elevated baPWV and 499 developed albuminuria.In comparison with the non-MAFLD group,the multivariable adjusted odds ratio(OR)of MAFLD group for new-onset elevated baPWV was 1.25(95%confidence interval(CI)1.01–1.55)and 1.35(95%CI 1.07–1.70)for albuminuria.Participants without NAFLD but diagnosed according to MAFLD definition were associated with higher risk of incident albuminuria(OR 1.77;95%CI 1.07–2.94).Patients with MAFLD with high value of hepamet fibrosis score or poor-controlled diabetes had higher risk of elevated baPWV or albuminuria.In conclusion,MAFLD was associated with new-onset elevated baPWV and albuminuria independently of body mass index,waist circumference,and hip circumference.Individuals without NAFLD but diagnosed as MAFLD had high risk of albuminuria,supporting that MAFLD criteria would be practical for the evaluation of long-term risk of subclinical atherosclerosis among fatty liver patients.