The Pumilio RNA-binding protein APUM24 regulates seed maturation by fine-tuning the BPM-WRI1 module in Arabidopsis

Pumilio RNAbindingproteinsparticipateinmes-senger RNA(mRNA)degradation and t ranslational repression,but their roles in plant development are largely unclear.Here,we show that Arabidopsis PUMILIO PROTEIN24(APUM24),an atypical Pumiliohomology domaincontaining protein,plays an im-portant part in regulating seed maturation,a major stage of plant development.APUM24 is strongly expressed in maturing seeds.Reducing APUM24 expression resulted in abnormal seed maturation,wrinkled seeds,and lower seed oil contents,and APUM24 knockdown resulted in lower levels of WRINKLED 1(WRI1),a key transcription factor con-trolling seed oil accumulation,and lower expression of WRI1 target genes.APUM24 reduces the mRNA stability of BTB/POZMATH(BPM)family genes,thus decreasing BPM protein levels.BPM is responsible for the 26S proteasomemediated degradation of WRI1 and has important functions in plant growth and development.The 3′untranslated regions of BPM family genes contain putative Pumilio response elements(PREs),which are bound by APUM24.Re-duced BPM or increased WRI1 expression rescued the decient seed maturation of apum242 knock-down mutants,and APUM24 overexpression re-sulted in increased seed size and weight.Therefore,APUM24 is crucial to seed maturation through its action as a positive regulatornetuning the BPMWRI1 module,making APUM24 apromising target for breeding strategies to increase crop yields.

Reprogramming plant specialized metabolism by manipulating protein kinases

Being sessile,plants have evolved sophisticated mechanisms to balance between growth and defense to survive in the harsh environment.The transition from growth to defense is commonly achieved by factors,such as protein kinases(PKs)and transcription factors,that initiate signal transduction and regulate specialized metabolism.Plants produce an array of lineage-specific specialized metabolites for chemical defense and stress tolerance.Some of these molecules are also used by humans as drugs.However,many of these defense-responsive metabolites are toxic to plant cells and inhibitory to growth and development.Plants have,thus,evolved complex regulatory networks to balance the accumulation of the toxic metabolites.Perception of external stimuli is a vital part of the regulatory network.Protein kinase-mediated signaling activates a series of defense responses by phosphorylating the target pro-teins and translating the stimulus into downstream cellular signaling.As biosynthesis of specialized metabolites is triggered when plants perceive stimuli,a possible connection between PKs and spe-cial ized meta bolism is well recognized.However,the roles of PKs in plant specialized metabolism have not received much attention until recently.Here,we summarize the recent advances in understanding PKs in plant specialized metabolism.We aim to highlight how the stimulatory signals are transduced,leading to the biosynthesis of corresponding metabolites.We discuss the post-translational regulation of specialized metabolism and provide insights into the mechanisms by which plants respond to the external signals.In addition,we propose possible strategies to increase the production of plant spe-cial ized metabolites in biotechnological applications using PKs.