In the context of global climate change and efforts toward “carbon peak and carbon neutrality,” forest resource protection and restoration have become fundamental to ecological civilization. The genetic improvement of trees, as the primary component of forest ecosystems, holds strategic importance for ecological security, resource supply, and carbon neutrality. Traditional tree breeding techniques, including selective and hybrid breeding, have established robust technical systems through extensive practice. However, these methods face limitations such as extended cycles, reduced efficiency, and constrained genetic gains in meeting contemporary requirements. Modern biotechnologies, including genomic selection (GS), gene editing (CRISPR/Cas9), and marker-assisted selection (MAS), substantially enhance the precision and efficiency of genetic improvement. Nevertheless, exclusive reliance on either traditional or modern methods proves insufficient for addressing complex environmental adaptation and rapid breeding requirements. Consequently, the integration of traditional breeding with modern biotechnology to develop intelligent, sustainable, and efficient breeding strategies has emerged as a central focus in tree genetics and breeding. An integrated “step-by-step” approach warrants promotion, supported by a multi-source data sharing platform, an optimized core germplasm repository, and a “climate-soil-genotype” matching model to facilitate the region-specific deployment of improved varieties.

Somatic embryogenesis in plants occurs via direct or indirect routes. In indirect somatic embryogenesis, embryos initiate from callus. The detachment of these embryos from callus is a critical step for plantlet recovery. Most reviews focus only on embryo induction. This review focuses specifically on the detachment stage. We examine how programmed cell death (PCD) drives this physical release. Cell death occurs in boundary callus cells and the suspensor. It does not destroy the developing embryo proper. PCD performs three main tasks. It dissolves middle lamella pectins. It removes the temporary suspensor. And it digests doomed cells to recycle nutrients for the embryo. Key proteases such as metacaspases execute this death program, with vacuolar processing enzymes representing candidate execution proteases. Epigenetic marks and transcription factors restrict cell death to the boundary. We also discuss practical ways to regulate PCD in tissue culture.

Drought stress significantly impairs plant growth and productivity, which triggers complex adaptive responses mediated by diverse gene families. Among these, the TOPLESS (TPL)/TPL-related (TPR) family of transcriptional corepressors plays a crucial role by recruiting epigenetic modifiers through interactions with EAR motif-containing proteins. However, genome-wide studies of this corepressor family and its associated regulatory networks with EAR motif-containing repressors remain limited. This study aimed to characterize the TPL/TPR transcriptional corepressor family in Populus ussuriensis Kom., elucidate their regulatory networks with EAR motif-containing repressors, and validate their functional roles in drought stress adaptation. To this end, we identified 21 TPL/TPR genes in P. ussuriensis (PuTPLs), classified them into five subfamilies, and found they are evolutionarily conserved with Arabidopsis thaliana and Populus trichocarpa, harboring characteristic CTLH and WD40 domains. Given that TPL/TPR proteins are recruited by transcription factors containing repression motifs, we constructed a putative TPL/TPR-EAR motif interaction network representing a core paradigm of negative regulation. Expression profiling under drought stress showed significant upregulation of most PuTPLs in a tissue-specific and temporal manner. Functional validation using transgenic P. ussuriensis lines overexpressing five PuTPLs demonstrated enhanced drought tolerance, evidenced by reduced electrolyte leakage and malondialdehyde content and increased proline accumulation. Our study provides the first comprehensive genome-wide analysis of the TPL/TPR family in P. ussuriensis, establishes a core EAR-mediated negative regulatory network, and validates the critical role of these genes in drought stress adaptation, providing valuable resources for future mechanistic research and breeding of stress-resistant trees.