Plant regeneration in the new era:from molecular mechanisms to biotechnology applications

Plants or tissues can be regenerated through various pathways.Like animal regeneration,cell totipotency and pluripotency are the molecular basis of plant regeneration.Detailed systematic studies on Arabidopsis thaliana gradually unravel the fundamental mechanisms and principles underlying plant regeneration.Specifically,plant hormones,cell division,epigenetic remodeling,and transcription factors play crucial roles in reprogramming somatic cells and reestablishing meristematic cells.Recent research on basal non-vascular plants and monocot crops has revealed that plant regeneration differs among species,with various plant species using distinct mechanisms and displaying significant differences in regenerative capacity.Conducting multi-omics studies at the single-cell level,tracking plant regeneration processes in real-time,and deciphering the natural variation in regenerative capacity will ultimately help understand the essence of plant regeneration,improve crop regeneration efficiency,and contribute to future crop design.

Enhancing wheat regeneration and genetic transformation through overexpression of TaLAX1

In the realm of genetically transformed crops,the process of plant regeneration holds utmost significance.However,the low regeneration efficiency of several wheat varieties currently restricts the use of genetic transformation for gene functional analysis and improved crop production.This research explores overex-pression of TaLAX PANICLE1(TaLAX1),which markedly enhances regeneration efficiency,thereby boost-ing genetic transformation and genome editing in wheat.Particularly noteworthy is the substantial increase in regeneration efficiency of common wheat varieties previously regarded as recalcitrant to genetic trans-formation.Our study shows that increased expression of TaGROWTH-REGULATING FACTOR(TaGRF)genes,alongside that of their co-factor,TaGRF-INTERACTING FACTOR 1(TaGIF1),enhances cytokinin accumulation and auxin response,which may play pivotal roles in the improved regeneration and transfor-mation of TaLAX1-overexpressing wheat plants.Overexpression of TaLAX1 homologs also significantly in-creases the regeneration efficiency of maize and soybean,suggesting that both monocot and dicot crops can benefit from this enhancement.Ourfindings shed light on a gene that enhances wheat genetic trans-formation and elucidate molecular mechanisms that potentially underlie wheat regeneration.

Application of Wox2a in transformation of recalcitrant maizegenotypes

The genetic transformation plays an important role in plant gene functional analysis and its geneticimprovement. However, only a limited number of maize germplasms can be routinely transformed. Themaize gene Wuschel-like homeobox protein 2a (Wox2a) was shown to play a crucial role in promotingthe formation of embryonic cells and enhancing the efficiency of genetic transformation in maize. Thiscommentary discusses the mechanism by which the Wox2a gene contributes to the variation inembryogenic tissue culture response among different maize inbred lines. In addition, the frequency andintensity of Wox2a or Wus2/Bbm vector-induced somatic embryogenesis was also discussed. Theapplication of Wox2a in transformation of recalcitrant maize genotypes could well accelerate thedevelopment of maize genetic improvement.

Plant cell totipotency: Insights into cellular reprogramming

Plant cells have a powerful capacity in their propagation to adapt to environmental change, given that a single plant cell can give rise to a whole plant via somatic embryogenesis without the need for fertilization. The reprogramming of somatic cells into totipotent cells is a critical step in somatic embryogenesis. This process can be induced by stimuli such as plant hormones, transcriptional regulators and stress. Here, we review current knowledge on how the identity of totipotent cells is determined and the stimuli required for reprogramming of somatic cells into totipotent cells. We highlight key molecular regulators and associated networks that control cell fate transition from somatic to totipotent cells. Finally,we pose several outstanding questions that should be addressed to enhance our understanding of the mechanisms underlying plant cell totipotency.

Regulation of cell reprogramming by auxin during somatic embryogenesis

How somatic cells develop into a whole plant is a central question in plant developmental biology.This powerful ability of plant cells is recognized as their totipotency.Somatic embryogenesis is an excellent example and a good research system for studying plant cell totipotency.However,very little is known about the molecular basis of cell reprogramming from somatic cells to totipotent cells in this process.During somatic embryogenesis from immature zygotic embryos in Arabidopsis,exogenous auxin treatment is required for embryonic callus formation,but removal of exogenous auxin inducing endogenous auxin biosynthesis is essential for somatic embryo(SE)induction.Ectopic expression of specific transcription factor genes,such as "LAFL" and BABY BOOM(BBM),can induce SEs without exogenous growth regulators.Somatic embryogenesis can also be triggered by stress,as well as by disruption of chromatin remodeling,including PRC2-mediated histone methylation,histone deacetylation,and PKL-related chromatin remodeling.It is evident that embryonic identity genes are required and endogenous auxin plays a central role for cell reprogramming during the induction of SEs.Thus,we focus on reviewing the regulation of cell reprogramming for somatic embryogenesis by auxin.

AtNSF regulates leaf serration by modulating intracellular trafficking of PIN1 in Arabidopsis thaliana

In eukaryotes,N-ethylmaleimide-sensitive factor(NSF)is a conserved AAA+ATPase and a key component of the membrane trafficking machinery that promotes the fusion of secretory vesicles with target membranes.Here,we demonstrate that the Arabidopsis thaliana genome contains a single copy of NSF,At NSF,which plays an essential role in the regulation of leaf serration.The At NSF knock-down mutant,atnsf-1,exhibited more serrations in the leaf margin.Moreover,polar localization of the PINFORMED1(PIN1)auxin efflux transporter was diffuse around the margins of atnsf-1 leaves and root growth was inhibited in the atnsf-1 mutant.More PIN1-GFP accumulated in the intracellular compartments of atnsf-1 plants,suggesting that At NSF is required for intracellular trafficking of PIN between the endosome and plasma membrane.Furthermore,the serration phenotype was suppressed in the atnsf-1 pin1-8 double mutant,suggesting that At NSF is required for PIN1-mediated polar auxin transport to regulate leaf serration.The CUPSHAPED COTYLEDON2(CUC2)transcription factor gene is up-regulated in atnsf-1 plants and the cuc2-3 single mutant exhibits smooth leaf margins,demonstrating that At NSF also functions in the CUC2 pathway.Our results reveal that At NSF regulates the PIN1-generated auxin maxima with a CUC2-mediated feedback loop to control leaf serration.

Pattern analysis of stem cell differentiation during in vitro Arabidopsis organogenesis

Plant somatic cells have the capability to switch their cell fates from differentiated to undifferen-tiated status under proper culture conditions,which is designated as totipotency.As a result,plant cells can easily regenerate new tissues or organs from a wide variety of explants.However,the mechanism by which plant cells have such remarkable regeneration ability is still largely unknown.In this study,we used a set of meristem-specific marker genes to analyze the patterns of stem cell differentiation in the processes of somatic embryogenesis as well as shoot or root organogenesis in vitro.Our studies furnish preliminary and important information on the patterns of the de novo stem cell differentiation during various types of in vitro organogenesis.