Identification of birch lncRNAs and mRNAs responding to salt stress and characterization of functions of lncRNA

Long noncoding RNAs(lncRNAs)are important in abiotic stress tolerance.Here,we identified salt-responsive genes and lncRNAs in the roots and leaves of Betula platyphylla Suk.(birch),and characterized their lncRNAs functions.In total,2660 mRNAs and 539 lncRNAs responding to salt treatment were identified using RNA-seq.The salt-responsive genes were substantially enriched in‘cell wall biogenesis’and‘wood development’in the roots and were enriched in‘photosynthesis’and‘response to stimulus’in the leaves.Meanwhile,the potential target genes of the salt-responsive lncRNAs in roots and leaves were both enriched in‘nitrogen compound metabolic process’and‘response to stimulus’.We further built a method for quickly identifying abiotic stress tolerance of lncRNAs,which employed transient transformation for overexpression and knock-down of the lncRNA,enabling gain-and loss-of-function analysis.Using this method,11 randomly selected salt-responsive lncRNAs were characterized.Among them,six lncRNAs confer salt tolerance,two lncRNAs confer salt sensitivity,and the other three lncRNAs are not involved in salt tolerance.In addition,a lncRNA,LncY1,was further characterized,which improves salt tolerance by regulating two transcription factors,BpMYB96 and BpCDF3.Taken together,our results suggested that lncRNAs play important roles in the salt response of birch plants.

Histological and single-nucleus transcriptome analyses reveal the specialized functions of ligular sclerenchyma cells and key regulators of leaf angle in maize

Leaf angle(LA)is a crucial factor that affects planting density and yield in maize.However,the regulatory mechanisms underlying LA formation remain largely unknown.In this study,we performed a comparative histological analysis of the ligular region across various maize inbred lines and revealed that LA is significantly influenced by a two-step regulatory process involving initial cell elongation followed by subsequent lignification in the ligular adaxial sclerenchyma cells(SCs).Subsequently,we performed both bulk and single-nucleus RNA sequencing,generated a comprehensive transcriptomic atlas of the ligular region,and identified numerous genes enriched in the hypodermal cells that may influence their specialization into SCs.Furthermore,we functionally characterized two genes encoding atypical basic-helix-loop-helix(bHLH)transcription factors,bHLH30 and its homolog bHLH155,which are highly expressed in the elongated adaxial cells.Genetic analyses revealed that bHLH30 and bHLH155 positively regulate LA expansion,and molecular experiments demonstrated their ability to activate the transcription of genes involved in cell elongation and lignification of SCs.These findings highlight the specialized functions of ligular adaxial SCs in LA regulation by restricting further extension of ligular cells and enhancing mechanical strength.The transcriptomic atlas of the ligular region at single-nucleus resolution not only deepens our understanding of LA regulation but also enables identification of numerous potential targets for optimizing plant architecture in modern maize breeding.