SMALL KERNEL4 is required for mitochondrial cox1 transcript editing and seed development in maize

In land plants,cytidine-to-uridine(C-to-U)editing of organellar transcripts is an important posttranscriptional process,which is considered to remediate DNA genetic mutations to restore the coding of functional proteins.Pentatricopeptide repeat(PPR)proteins have key roles in C-to-U editing.Owing to its large number,however,the biological functions of many PPR proteins remain to be identified.Through characterizing a small kernel4(smk4)mutant,here we report the function of Smk4 and its role in maize growth and development.Null mutation of Smk4 slows plant growth and development,causing small plants,delayed flowering time,and small kernels.Cloning revealed that Smk4 encodes a new E-subclass PPR protein,and localization indicated that SMK4 is exclusively localized in mitochondria.Loss of Smk4 function abolishes C-to-U editing at position 1489 of the cytochrome c oxidase1(cox1)transcript,causing an amino acid change from serine to proline at 497 in Cox1.Cox1 is a core component of mitochondrial complex IV.Indeed,complex IV activity is reduced in the smk4,along with drastically elevated expression of alternative oxidases(AOX).These results indicate that SMK4 functions in the C-to-U editing of cox1-1489,and this editing is crucial for mitochondrial complex IV activity,plant growth,and kernel development in maize.

Translational Regulation of Metabolic Dynamics during Effector-Triggered Immunity

Recent studies have shown that global translational reprogramming is an early activation event in pattern-triggered immunity,when plants recognize microbe-associated molecular patterns.However,it is not fully known whether translational regulation also occurs in subsequent immune responses,such as effector-triggered immunity(ETI).In this study,we performed genome-wide ribosome profiling in Arabidopsis upon RPS2-mediated ETI activation and discovered that specific groups of genes were translationally regulated,mostly in coordination with transcription.These genes encode enzymes involved in aromatic amino acid,phenylpropanoid,camalexin,and sphingolipid metabolism.The functional significance of these components in ETI was confirmed by genetic and biochemical analyses.Our findings provide new insights into diverse translational regulation of plant immune responses and demonstrate that translational coordination of metabolic gene expression is an important strategy for ETI.

The BZR1-EDS1 module regulates plant growth-defense coordination

Plants have developed sophisticated strategies to coordinate growth and immunity,but our understanding of the underlying mechanism remains limited.In this study,we identified a novel molecular module that reg-ulates plant growth and defense in both compatible and incompatible infections.This module consisted of BZR1,a key transcription factor in brassinosteroid(BR)signaling,and EDS1,an essential positive regulator of plant innate immunity.We found that EDS1 interacts with BZR1 and suppresses its transcriptional activ-ities.Consistently,upregulation of EDS1 function by a virulent Pseudomonas syringae strain or salicylic acid treatment inhibited BZR1-regulated expression of BR-responsive genes and BR-promoted growth.Furthermore,we showed that the cytoplasmic fraction of BZR1 positively regulates effector-triggered im-munity(ETI)controlled by the TIR-NB-LRR protein RPS4,which is attenuated by BZR1's nuclear transloca-tion.Mechanistically,cytoplasmic BZR1 facilitated AvrRps4-triggered dissociation of EDS1 and RPS4 by binding to EDS1,thus leading to efficient activation of RPS4-controlled ETI.Notably,transgenic expression of a mutant BZR1 that accumulates exclusively in the cytoplasm improved pathogen resistance without compromising plant growth.Collectively,these results shed new light on plant growth-defense coordina-tion and reveal a previously unknown function for the cytoplasmic fraction of BZR1.The BZR1-EDS1 mod-ule may be harnessed for the simultaneous improvement of crop productivity and pathogen resistance.

Wheat genomic study for genetic improvement of traits in China

Bread wheat(Triticum aestivum L.)is a major crop that feeds 40%of the world’s population.Over the past several decades,advances in genomics have led to tremendous achievements in understanding the origin and domestication of wheat,and the genetic basis of agronomically important traits,which promote the breeding of elite varieties.In this review,we focus on progress that has been made in genomic research and genetic improvement of traits such as grain yield,end-use traits,flowering regulation,nutrient use efficiency,and biotic and abiotic stress responses,and various breeding strategies that contributed mainly by Chinese scientists.Functional genomic research in wheat is entering a new era with the availability of multiple reference wheat genome assemblies and the development of cutting-edge technologies such as precise genome editing tools,highthroughput phenotyping platforms,sequencing-based cloning strategies,high-efficiency genetic transformation systems,and speed-breeding facilities.These insights will further extend our understanding of the molecular mechanisms and regulatory networks underlying agronomic traits and facilitate the breeding process,ultimately contributing to more sustainable agriculture in China and throughout the world.