SlBEL11 regulates flavonoid biosynthesis,thus fine-tuning auxin efflux to prevent premature fruit drop in tomato

Auxin regulates flower and fruit abscission,but how developmental signals mediate auxin transport in abscission remains unclear.Here,we reveal the role of the transcription factor BEL1-LIKE HOMEODOMAIN11(SlBEL11)in regulating auxin transport during abscission in tomato(Solanum lycopersicum).SlBEL11 is highly expressed in the fruit abscission zone,and its expression increases during fruit development.Knockdown of SlBEL11 expression by RNA interference(RNAi)caused premature fruit drop at the breaker(Br)and 3d post-breaker(Br+3)stages of fruit development.Transcriptome and metabolome analysis of SlBEL11-RNAi lines revealed impaired flavonoid biosynthesis and decreased levels of most flavonoids,especially quercetin,which functions as an auxin transport inhibitor.This suggested that SlBEL11 prevents premature fruit abscission by modulating auxin efflux from fruits,which is crucial for the formation of an auxin response gradient.Indeed,quercetin treatment suppressed premature fruit drop in SlBEL11-RNAi plants.DNA affinity purification sequencing(DAP-seq)analysis indicated that SlBEL11 induced expression of the transcription factor gene SlMYB111 by directly binding to its promoter.Chromatin immunoprecipitation-quantitative polymerase chain reaction and electrophoretic mobility shift assay showed that S.lycopersicum MYELOBLASTOSIS VIRAL ONCOGENE HOMOLOG111(SlMYB111)induces the expression of the core flavonoid biosynthesis genes SlCHS1,SlCHI,SlF3H,and SlFLS by directly binding to their promoters.Our findings suggest that the SlBEL11-SlMYB111 module modulates flavonoid biosynthesis to fine-tune auxin efflux from fruits and thus maintain an auxin response gradient in the pedicel,thereby preventing premature fruit drop.

Dynamic control of lipid provisioning in plant-fungal symbiosis

Arbuscular mycorrhizal(AM)fungi form a type of endomycorrhiza that helps plants capture nutrients from the soil.Lipid provisioning plays a critical role in maintaining the AM fungi within the plant cortical cells during AM symbiosis.The coordination of lipid provisioning with AM symbiosis is regulated by the lysin motif(LysM)and leucine-rich repeat receptor-like kinases(RLKs),including DOES NOT MAKE INFECTIONS 2(DMI2),through transcriptional programming(Shi et al.,2023).However,key components of the complete signaling pathway remain to be identified.

CRISPR-mediated BnaIDAediting prevents silique shattering, floral organ abscission, and spreading of Sclerotinia sclerotiorum in Brassica napus

Dear Editor,Rapeseed(Brassica napus)oil is a major source of vegetable oil around the world.Stem rot disease caused by the necrotrophic fungus Sclerotinia sclerotiorum and silique shattering during harvest are two major contributors to yield loss in B.napus(Zhang et al.,2021).Infection by S.sclerotiorum occurs when ascospores land on detached petals where they germinate and form mycelia that ultimately infects the leaves(Ding et al.,2021).Consistent with this mode of infection,reduced damage from stem rot has been achieved by generating apetalous rapeseed that are resistant to petal-mediated infection(Yu et al.,2016).We propose that preventing petal shedding should also reduce leaf infections.Moreover,attached floral organs will promote rapeseed flower tourism and provide an additional economic benefit.

Ligand deprivation activates receptor signaling

Signaling peptides,together with their receptor kinases and proteins,are involved in a wide range of processes related to plant growth,development,and stress responses.In Arabidopsis,over 1000 different peptides and 251 leucine-rich repeat receptorkinases(LRR-RKs)were identified.

Structural basis of RLP activation by a pathogen glycoside hydrolase

Pathogen-associated molecular patterns(PAMPs)are recognized by host-encoded,cell-surface-localized,pattern-recognition receptors.In plants,pattern-recognition receptors consist of two kinds of proteins,the receptor-like kinases(RLKs)and the receptor-like proteins(RLPs).Compared with RLKs,RLPs lack an intracellular kinase domain,thus requiring co-receptors to initiate intracellular immune responses.PAMP recognition by RLKs with extracellular leucine-rich repeat(LRR)domains has been extensively studied,with structures of several PAMP-RLK pairs solved;however,the mechanism of how RLPs are activated is not well understood.

O2-ZmGRAS11 coordinates cell expansion and endosperm filling

Maize(Zea mays),a major crop for food and feed,is grown world-wide with a high annual yield.The grain size and weight of maize are mainly determined by starch and storage proteins that are actively synthesized during endosperm filling.During early endo-sperm development,the maize endosperm undergoes a series of cell division,differentiation,and expansion events.Cell division and expansion determine the number and size of endosperm cells,respectively,influencing the final grain size and yield.While cell division mainly occurs during early endosperm development,cell expansion occurs continuously,particularly during the endo-sperm filling stage when starchy endosperm cells are enlarged with storage metabolites.Despite several key genes involved in the regulation of either endosperm filling or cell expansion being identified,how these two processes are coordinated remains elusive.

ITPK1 functions as both a kinase and an ADP phosphotransferase in Pi signaling

Phosphorus is one of mineral elements essential for plant growth and development.To cope with low phosphate(Pi)conditions,plants have evolved complex signaling mechanisms including the inositol phosphate(InsP)signaling pathway in which the phosphate starvation response(PHR)transcription factors control the expression of Pi starvation-induced genes in a Pi-dependent manner.The activities of PHRs are regulated by their interactions with SPX proteins that act as receptors for inositol pyrophosphates(PP-lnsPs),such as lnsP7 and lnsP8.In plants,the syn thesis of lnsP8 is mediated by the bifunctional kinase/phosphatase enzymes,VIH1 and VIH2.However,lnsP6 kinases responsible for the synthesis of lnsP7 in plants have long remained elusive.

OsEDRI has non-canonical scaffold function in regulating MAPK cascade in plant immunity

Mitogen-activated protein kinase(MAPK)cascades,typically composed of MAPK kinase kinases(MAPKKKs),MAPK kinases(MAPKKs),and MAPKs(MPKs),are highly conserved signaling modules that regulate various biological processes in plant development and stress response.The MAPKKK family in plants is divided into two subfamilies:MEKK-like and Raf-like kinases.The MEKK-like kinases are known to activate the downstream MAPK modules through sequential phosphorylation(Meng and Zhang 2013).In contrast,the mechanism of Raf-like MAPKKKs in the regulation of MAPK cascades is not fully understood.

Hijacking Plant Receptor by Nematode-Derived Peptide Mimics

The receptor-like kinase(RLK)FERONIA(FER)and its peptide ligands,called RALFs(Rapid ALkalinization Factors),function as signaling modules to control plant growth and development,stress responses,and plant immunity.Interestingly,the fungal pathogen,Fusarium oxysporum,can produce RALF mimics that interact with plant FER to promote fungal infection and multiplication(Masachis et al.,2016).Plant-parasitic nematodes such as root-knot nematodes(RKNs)cause worldwide crop damage;however,whether RNKs encode RALF peptide mimics and how they may facilitate RKN infection of host plants remain unclear.

Small Peptides Raising in Plants

Small signaling peptides or so-called peptide hormones(Figure 1)in plants ranging from 5 to 75 amino acids in length are important signaling molecules for both plant growth and responses to abiotic and biotic stimuli(Olsson et al.,2019).In addition,plants also contain many other types of small peptides.Compared with conventional peptides(CPs),which are derived from annotated coding sequences(CDSs)or open reading frames,plant genomes also encode non-conventional peptides(NCPs)derived from unannotated CDSs,including introns,UTRs,and intergenic regions,as well as different reading frames of annotated CDSs.