Gibberellic acid-stimulated Arabidopsis (GASA) proteins, as cysteine-rich peptides (CRPs), play roles in development and reproduction and biotic and abiotic stresses. Although the GASA gene family has been identified in plants, the knowledge about GASAs in Populus euphratica, the woody model plant for studying abiotic stress, remains limited. Here, we referenced the well-sequenced Populus trichocarpa genome, and identified the GASAs in the whole genome of P. euphratica and P. trichocarpa. 21 candidate genes in P. trichocarpa and 19 candidate genes in P. euphratica were identified and categorized into three subfamilies by phylogenetic analysis. Most GASAs with signal peptides were located extracellularly. The GASA genes in Populus have experienced multiple gene duplication events, especially in the subfamily A. The evolution of the subfamily A, with the largest number of members, can be attributed to whole-genome duplication (WGD) and tandem duplication (TD). Collinearity analysis showed that WGD genes played a leading role in the evolution of GASA genes subfamily B. The expression patterns of P. trichocarpa and P. euphratica were investigated using the PlantGenIE database and the real-time quantitative PCR (qRT-PCR), respectively. GASA genes in P. trichocarpa and P. euphratica were mainly expressed in young tissues and organs, and almost rarely expressed in mature leaves. GASA genes in P. euphratica leaves were also widely involved in hormone responses and drought stress responses. GUS activity assay showed that PeuGASA15 was widely present in various organs of the plant, especially in vascular bundles, and was induced by auxin and inhibited by mannitol dramatically. In summary, this present study provides a theoretical foundation for further research on the function of GASA genes in P. euphratica.

Propagation through cuttings is a well-established and effective technique for plant multiplication. This study explores the regeneration of poplar roots using spatial transcriptomics to map a detailed developmental trajectory. Mapping of the time-series transcriptome data revealed notable alterations in gene expression during root development, particularly in the activation of cytokinin-responsive genes. Our analysis identified six distinct clusters during the second and third stages, each corresponding to specific anatomical regions with unique gene expression profiles. Auxin response cis-elements (AuxREs) were prevalent in the promoters of these cytokinin-responsive genes, indicating a regulatory interplay between auxin and cytokinin. Pseudo-temporal trajectory analysis mapped the differentiation from cambium cells to root primordium cells, revealing a complex pattern of cell differentiation. SAC56 and LOS1 emerged as potential novel biomarkers for enhancing root regeneration, with distinct spatial expression patterns confirmed by in situ hybridization. This comprehensive spatial analysis enhances our understanding of the molecular interactions driving root regeneration and provides insights for improving plant propagation techniques.

The poplar is a model system for research on wood plant biology. An establishment of an efficient poplar regeneration system (PRS) plays a key role in the molecular breeding of wood plants. At present, most established PRSs are based on orthogonal experiments of previous research data. However, such an experiment is complex, time-consuming, and inefficient for various poplar subspecies. Therefore, an efficient solution to the establishment of PRSs is urgent. In this study, the triploid white poplar (Populus tomentosa ‘YiXianCiZhu B385′) was used as an experimental material to establish a leaf-based regeneration system. Firstly, different concentrations of hormones were added into the medium for the differentiation, stretching, and rooting of leaves, and the electrical conductivity of the medium was measured by a conductivity meter. Secondly, the optimal hormone concentrations for differentiation, stretching, and rooting were obtained by wavelet analysis. Finally, the Electrical Signal Conduction Characterization Model (ESCCM) of different hormone concentrations in the differentiation, stretching, and rooting of poplars was established. The result showed that the ESCCM improves the efficiency of PRSs, and this provides new insight and theory in molecular breeding. The ESCCM also provides the possibility of an automated establishment of a PRS.