Contribution of phenylpropanoid metabolism to plant development and plant–environment interactions

Phenylpropanoid metabolism is one of the most important metabolisms in plants, yielding more than 8,000 metabolites contributing to plant development and plant-environment interplay.Phenylpropanoid metabolism materialized during the evolution of early freshwater algae that were initiating terrestrialization and land plants have evolved multiple branches of this pathway, which give rise to metabolites including lignin, flavonoids, lignans, phenylpropanoid esters, hydroxycinnamic acid amides, and sporopollenin.Recent studies have revealed that many factors participate in the regulation of phenylpropanoid metabolism, and modulate phenylpropanoid homeostasis when plants undergo successive developmental processes and are subjected to stressful environments. In this review, we summarize recent progress on elucidating the contribution of phenylpropanoid metabolism to the coordination of plant development and plant–environment interaction, and metabolic flux redirection among diverse metabolic routes. In addition, our review focuses on the regulation of phenylpropanoid metabolism at the transcriptional, post-transcriptional, post-translational,and epigenetic levels, and in response to phytohormones and biotic and abiotic stresses.

Translational Regulation of Plant Response to High Temperature by a Dual-Function tRNAHls Guanylyltransferase in Rice

As sessile organisms,plants have evolved numerous strategies to acclimate to changes in environmental temperature.However,the molecular basis of this acclimation remains largely unclear.In this study we identified a tRNAHis guanylyltransferase,AET1,which contributes to the modification of pre-tRNAH,s and is required for normal growth under high-temperature conditions in rice.Interestingly,AET1 possibly interacts with both RACK1A and elF3h in the endoplasmic reticulum.Notably,AET1 can directly bind to OsARF mRNAs including the uORFs of OsARF19 and OsARF23,indicating that AET1 is associated with translation regulation.Furthermore,polysome profiling assays suggest that the translational status remains unaffected in the aet1 mutant,but that the translational efficiency of OsARF19 and OsARF23 is reduced;moreover,OsARF23 protein levels are obviously decreased in the aet1 mutant under high temperature,implying that AET1 regulates auxin signaling in response to high temperature.Ourfindings provide new insights into the molecular mechanisms whereby AET1 regulates the environmental temperature response in rice by playing a dual role in tRNA modification and translational control.

Tillering and small grain 1 dominates the tryptophan aminotransferase family required for local auxin biosynthesis in rice

Auxin is a crucial phytohormone,controlling multiple aspects of plant growth and responses to the changing environment.However,the role of local auxin biosynthesis in specific developmental programs remains unknown in crops.This study characterized the rice tillering and small grain 1(tsg1)mutant,which has more tillers but a smaller panicle and grain size resulting from a reduction in endogenous auxin.TSG1 encodes a tryptophan aminotransferase that is allelic to the FISH BONE(FIB)gene.The tsg1 mutant showed hypersensitivity to indole-3-acetic acid and the competitive inhibitor of aminotransferase,L-kynurenine.TSG1 knockout resulted in an increased tiller number but reduction in grain number and size,and decrease in height.Meanwhile,deletion of the TSG1 homologs OsTAR1,Os TARL1,and OsTARL2 caused no obvious changes,although the phenotype of the TSG1/Os TAR1 double mutant was intensified and infertile,suggesting gene redundancy in the rice tryptophan aminotransferase family.Interestingly,TSG1 and Os TAR1,but not Os TARL1 and OsTARL2,displayed marked aminotransferase activity.Meanwhile,subcellular localization was identified as the endoplasmic reticulum,while phylogenetic analysis revealed functional divergence of TSG1 and OsTAR1 from OsTARL1 and OsTARL2.These findings suggest that TSG1 dominates the tryptophan aminotransferase family,playing a prominent role in local auxin biosynthesis in rice.

Anα/βhydrolase family member negatively regulates salt tolerance but promotes flowering through three distinct functions in rice

Ongoing soil salinization drastically threatens crop growth,development,and yield worldwide.It is therefore crucial that we improve salt tolerance in rice by exploiting natural genetic variation.However,many salt-responsive genes confer undesirable phenotypes and therefore cannot be effectively applied to practical agricultural production.In this study,we identified a quantitative trait locus for salt tolerance from the African rice species Oryza glaberrima and named it as Salt Tolerance and Heading Date 1(STH1).We found that STH1 regulates fatty acid metabolic homeostasis,probably by catalyzing the hydrolytic degradation of fatty acids,which contributes to salt tolerance.Meanwhile,we demonstrated that STH1 forms a protein complex with D3 and a vital regulatory factor in salt tolerance,OsHAL3,to regulate the protein abundance of OsHAL3 via the 26S proteasome pathway.Furthermore,we revealed that STH1 also serves as a co-activator with the floral integrator gene Heading date 1 to balance the expression of the florigen gene Heading date 3a under different circumstances,thus coordinating the regulation of salt tolerance and heading date.Notably,the allele of STH1 associated with enhanced salt tolerance and high yield is found in some African rice accessions but barely in Asian cultivars.Introgression of the STH1HP46 allele from African rice into modern rice cultivars is a desirable approach for boosting grain yield under salt stress.Collectively,our discoveries not only provide conceptual advances on the mechanisms of salt tolerance and synergetic regulation between salt tolerance and flowering time but also offer potential strategies to overcome the challenges resulted from increasingly serious soil salinization that many crops are facing.