Pingdong Zhang

Polyploidization by forming diploid gametes is an important force driving diversification and speciation in plant evolution. The prevalence of polyploids i

Base excision repair (BER) is a critical pathway for repairing damaged DNA bases in cells; however, the mechanisms of protein recruitment and interaction in this pathway remain largely unexplored in higher plants. In this study, we used ‘84K’ poplar ( Populus alba × P. glandulosa ) as the experimental system and applied a low concentration of 5‐aminouracil (5‐AU) to induce DNA base lesions. Through transcriptome analysis and weighted gene co‐expression network analysis (WGCNA), we identified two key BER‐responsive genes: the DNA glycosylase family gene PagDMG6341 and the DNA polymerase δ subunit PagPOLD4 . PagDMG6341 was significantly upregulated during the arrest phase of 5‐AU treatment, whereas PagPOLD4 expression peaked during the subsequent release phase. RNA interference (RNAi) lines for each gene resulted in impaired growth and increased susceptibility to 5‐AU in ‘84K’ poplar, supporting their functional roles in DNA repair and development. To further investigate their potential interaction network, we performed yeast two‐hybrid (Y2H) screening, AlphaFold3‐based structural modelling, confirmatory Y2H, bimolecular fluorescence complementation (BiFC) assays, and luciferase complementation imaging (LCI) assays. These experiments demonstrated that a Transducin/WD40‐repeat‐like scaffold protein (PagWD40) interacts independently with both PagDMG6341 and PagPOLD4. The yeast three‐hybrid (Y3H) assay further showed that PagWD40 functions as a molecular scaffold, linking PagDMG6341 and PagPOLD4 to form a functional complex. This study reveals a new mechanism in which PagWD40 functions as a scaffold protein linking a DNA glycosylase with DNA polymerase δ in the plant BER pathway, thereby providing new insights into the organisation of plant DNA damage repair networks.

Key message This research develops a novel method for improving tetraploid induction efficiency in vitro by precisely identifying key cell cycle phases and optimizing synchronization treatments in ‘84 K’ poplar. Abstract Cell cycle asynchrony is a critical bottleneck in tetraploid in vitro induction efficiency. 5-Aminouracil (5-AU), a known cell cycle inhibitor, provides a strategy to enhance tetraploid induction efficiency. However, as 5-AU primarily targets S-phase cells and demonstrates cytotoxicity, improving tetraploid induction efficiency requires first accurately identifying the peak window of S-phase cell accumulation in the cultured tissue. Additionally, it is crucial to determine the appropriate concentration range of 5-AU to minimize toxicity to the cultured tissue. In this study, we developed a cell cycle synchronization strategy and evaluated its effect on tetraploid induction efficiency. Flow cytometry and EdU fluorescence labeling were used to track the cell cycle progression of ‘84 K’ poplar (Populus alba × P. glandulosa) leaves during in vitro culture. Our results showed that S-phase activity peaked between days 2 and 3 of differentiation, while the G2/M phase began on day 4. This defined the optimal synchronization window as days 2 to 3. Comet assays were conducted to evaluate DNA damage induced by 5-AU. The results showed that DNA fragmentation increased significantly at concentrations exceeding 1.7 mM. In contrast, at concentrations below 1.3 mM, comet assays indicated relatively low DNA damage, while flow cytometry analysis revealed suboptimal synchronization efficiency. Consequently, 1.5 mM was identified as the optimal concentration for synchronization induction. By applying this synchronization strategy, the tetraploid induction rate of ‘84 K’ poplar was increased to an average of 40.90%. Our results demonstrate that precise synchronization of the cell cycle, with minimal cytotoxicity, can significantly improve tetraploid induction efficiency.

In the poplar plantations, soil microorganisms—particularly key microbial taxa—can have a profound impact on plant growth through their responses to environmental changes. However, there remains a lack of understanding of how environmental factors drive microbial diversity and key taxa, and how these, in turn, affect poplar growth. This study investigated 6‐year‐old poplar plantations across three regions of the North China Plain (Beijing, Hebei, and Henan). Combined with high‐throughput cultivation and pot experiments, the growth‐promoting effects of culturable key microbial strains on poplars were assessed. The results showed significant differences in climate indices, poplar growth traits, soil physicochemical properties, and soil microbial communities among the plantation regions ( p < 0.05). A synthetic community comprising key strains ( Acinetobacter ‐Aa20, Bacillus ‐Aa15, Bacillus ‐Ba9, and Bacillus ‐Ab26) significantly promoted poplar seedling growth. The results indicated that mean annual precipitation and mean annual temperature influence soil nutrient availability, thereby affecting poplar growth. Key taxa may indirectly promote poplar growth by being recruited through soil nutrient dynamics. This study provides important ecological insights into the interaction mechanisms among environmental factors, plants, soil, and microorganisms in poplar plantation ecosystems.

The artificial induction of unreduced (2n) gametes, due to first division restitution (FDR) or second division restitution (SDR), is an important method to produce triploids in higher plants. It is crucial to evaluate the genetic composition and heterozygosity transmission of induced 2n gametes with different formation mechanisms. Here, we produced 110 triploids by pollinating the female inflorescence of Populus alba × P. glandulosa with gibberellin-induced 2n pollen of Populus bolleana. The genetic composition and heterozygosity of the induced 2n pollen were inferred from SSR marker analysis of the triploid offspring, using 27 primer pairs distributed across nine Populus chromosomes. This revealed that, among the 110 hybrid triploids, 70 triploids did originate from FDR-type 2n pollen and the other 40 from SDR-type 2n pollen. The FDR-type and SDR-type 2n pollen transmitted a substantially different level of parental heterozygosity (0.7545 and 0.3167, respectively) in P. bolleana. Additionally, compared with the low coefficient of variation (CV = 12.82%) for heterozygosity transmitted by FDR-type 2n pollen, there was much higher coefficient of variation (CV = 48.82%) for that transmitted by SDR-type 2n pollen. Our findings provide a valuable reference point for bolstering suitable applications of 2n gametes in future research, and can help foster new strategies of triploid breeding in plants. Not applicable.

Aneuploidy in plants commonly presents as large variations in morphology, physiology, biochemistry, and genetic effects owing to its karyotypic imbalance. In this study, the trait variations of 393 offspring obtained by pollinating Populus alla × Populus glandulosa ‘YXY 7’ (2n = 2x = 38) with Populus ‘Beilinxiongzhu 1#’ (2n = 3x = 57) were explored. The results showed several morphological variations in the cotyledons, including two (69.68%), three (24.07%), and four cotyledons (6.25%). Additionally, the progeny exhibited extensive segregation of ploidy levels, ranging from 38 to 74. Furthermore, seedlings with different chromosome numbers varied in growth traits and physiological activities during growth and development. The backcross progeny with 51–60 chromosomes had a significantly larger basal diameter and seedling height than those with other chromosome numbers. The phenotypic correlations between the traits indicated that the dose effect of the chromosomes significantly affected the basal diameter, petiole length, and leaf length, particularly with stomatal length and stomatal density. Weak and negative estimated correlations were observed between the physiological traits associated with photosynthesis and most of the studied traits. This study provides new genetic material with different chromosome compositions, which will contribute to analyzing chromosomal function and integrate the variations in chromosomal dosage into Populus breeding programs.

Genetic diversity analysis provides the scientific basis for the preservation, evaluation, and utilization of the germplasm resources of tree species. We explored the genetic diversity and structure of Populus tomentosa elite trees in North China using 13 nuclear microsatellite markers. We compared nine groups of accessions including 20 originating from Beijing (BJ), 122 from Hebei (HB), 20 from Shandong (SD), 113 from Henan (HN), 270 from Shanxi (SX), 54 from Shaanxi (SAX), 8 from Gansu (GS), 10 from Anhui (AH), and 6 from Jiangsu (JS). All of the studied primer pairs were polymorphic and generated 125 alleles. Analyses of molecular variance revealed that 79%, 14%, and 8% of the total variation was due to variations within the individual, among individuals, and among populations, respectively. Based on principal coordinate and STRUCTURE cluster analyses, individuals distributed in the southern region (HN, SAX, AH, and JS) were roughly classified into one group, while those distributed in the northeastern region (BJ, HB, and SD) and northwestern regions (SX) were separately divided into one group each. Moreover, the northwestern region included two-thirds of the SX trees, and the remainder were in the northeast region. By analyzing genetic diversity and structure within populations, individuals with different genetic backgrounds were screened for constituent training populations (TRS), including broad allelic variation for related traits. This ensures that the genomic prediction model can accurately capture genetic effects and provide reliable predictions across a broad spectrum of genetic backgrounds. Therefore, our results will benefit genome breeding technology.

Background: Artificial induction of polyploidy is the most common and effective way to improve the biological properties of Populus and develop new varieties of this tree. In this study, in order to confirm and expand earlier findings, we established a protocol using colchicine and based on an efficient shoot regeneration system of leaf blades to induce tetraploidy in vitro in three genotypes from diploid Populus hopeiensis. The stomatal characteristics, leaf blade size, and growth were evaluated for diploids and tetraploids of three genotypes. Results: We found that genotype, preculture duration, colchicine concentration, and colchicine exposure time had highly significant effects on the tetraploid induction rate. The optimal protocol for inducing tetraploidy in P. hopeiensis was to preculture leaf blades for 7 days and then treat them for 4 days with 40 mg/L colchicine. The tetraploid induction rates of genotypes BT1, BT3, and BT8 were 21.2, 11.4 and 16.7%, respectively. A total of 136 tetraploids were identified by flow cytometry analysis and somatic chromosome counting. The stomatal length, width, and density of leaf blades significantly differed between diploid and tetraploid plants. Compared with their diploid counterparts, the tetraploids produced larger leaf blades and had a slower growth rate. Our findings further document the modified morphological characteristics of P. hopeiensis following whole-genome duplication (e.g., induced tetraploidy). Conclusions: We established a protocol for in vitro induction of tetraploidy from diploid leaf blades treated with colchicine, which can be applied to different genotypes of P. hopeiensis.

Background: Triploid Populus tomentosa, a timber tree species, has been widely planted in northern China owing to its potential high yields and high wood quality. Though genetic variances in growth traits and wood properties have been reported across several planting sites, regional testing of triploid hybrid clones of P. tomentosa has not been conducted on a large scale. Results: Ten 5-year clonal trials were used to evaluate the inheritance of growth traits, to determine suitable deployment zones, and to identify optimal triploid clones at each experimental site to determine the clones that would be suitable at all sites. A total of 2,430 trees from nine triploid hybrid clones were sampled during the ten trials. The clonal and site effects and clone × site interactions were highly significant (P < 0.001) for all the studied growth and yield traits. The estimated repeatability of means for diameter at breast height (DBH) and tree height (H) was 0.83, which was slightly higher than for stem volume (SV) and estimated stand volume (ESV) (0.78). The Weixian (WX), Gaotang (GT), and Yanzhou (YZ) sites were each considered to be suitable deployment zones, and the Zhengzhou (ZZ), Taiyuan (TY), Pinggu (PG), and Xiangfen (XF) sites were found to be the optimal deployment zones. The TY and ZZ sites were the best discriminative environments, and the GT and XF sites were the best representative environments. GGE pilot analysis revealed that yield performance and stability were significantly different among all the studied triploid hybrid clones across the ten test sites. It was therefore necessary to develop a suitable triploid hybrid clone that could do well at each site. Taking into account both yield performance and stability, the triploid hybrid clone S2 was determined to be an ideal genotype. Conclusions: For triploid hybrid clones, the WX, GT, and YZ sites represented suitable deployment zones and the ZZ, TY, PG, and XF sites represented optimal deployment zones. Yield performance and stability were significantly different among all the studied triploid hybrid clones across the ten test sites. Developing a suitable triploid hybrid clone that could do well at all sites was therefore desirable.