@article{zhang_unraveling_2025,
	title = {Unraveling nitrogen uptake and metabolism: gene families, expression dynamics and functional insights in aspen ({Populus} tremula)},
	volume = {45},
	issn = {1758-4469},
	shorttitle = {Unraveling nitrogen uptake and metabolism},
	url = {https://doi.org/10.1093/treephys/tpaf099},
	doi = {10.1093/treephys/tpaf099},
	abstract = {The influence of nitrogen on wood formation is well established. To gain insight into the underlying molecular mechanism, we first identified genes in 14 gene families that are involved in nitrogen uptake and metabolism in European aspen (Populus tremula L.) genome annotation. Gene expression data from a de novo RNA sequencing (RNA-seq) analysis and data available from the AspWood database (plantgenie.org) provided putative candidate genes for the uptake of nitrate, ammonium and amino acids from the xylem sap as well as their further assimilation in the secondary xylem tissues of the stem. For a population-wide analysis of the nitrogen-related genes, we utilized RNA-seq data from the cambial region of the stems of 5-year-old aspen trees, representing 99 natural aspen accessions, and compared the expression of the nitrogen-related genes to stem diameter. Novel regulatory interactions were identified in expression quantitative loci and co-expression network analyses in these data. The expression of certain nitrate and amino acid transporters correlated negatively with stem diameter, suggesting that excessive nitrogen retrieval from the xylem sap suppresses radial growth of the stem. The expression of a glutamine synthetase correlated with the expression of these transporters, a link further supported by increased plant growth in transgenic glutamine synthetase overexpressing trees. This study provides insight into the genetic basis of nitrogen uptake and assimilation and its connection to wood formation, providing interesting targets for improving nitrogen-use efficiency and growth of aspen trees.},
	number = {13},
	urldate = {2025-12-05},
	journal = {Tree Physiology},
	author = {Zhang, Yupeng and Choudhary, Shruti and Renström, Anna and Luomaranta, Mikko and Chantreau, Maxime and Fleig, Verena and Gaboreanu, Ioana and Grones, Carolin and Nilsson, Ove and Robinson, Kathryn M and Tuominen, Hannele},
	month = nov,
	year = {2025},
	pages = {100--113},
}

The influence of nitrogen on wood formation is well established. To gain insight into the underlying molecular mechanism, we first identified genes in 14 gene families that are involved in nitrogen uptake and metabolism in European aspen (Populus tremula L.) genome annotation. Gene expression data from a de novo RNA sequencing (RNA-seq) analysis and data available from the AspWood database (plantgenie.org) provided putative candidate genes for the uptake of nitrate, ammonium and amino acids from the xylem sap as well as their further assimilation in the secondary xylem tissues of the stem. For a population-wide analysis of the nitrogen-related genes, we utilized RNA-seq data from the cambial region of the stems of 5-year-old aspen trees, representing 99 natural aspen accessions, and compared the expression of the nitrogen-related genes to stem diameter. Novel regulatory interactions were identified in expression quantitative loci and co-expression network analyses in these data. The expression of certain nitrate and amino acid transporters correlated negatively with stem diameter, suggesting that excessive nitrogen retrieval from the xylem sap suppresses radial growth of the stem. The expression of a glutamine synthetase correlated with the expression of these transporters, a link further supported by increased plant growth in transgenic glutamine synthetase overexpressing trees. This study provides insight into the genetic basis of nitrogen uptake and assimilation and its connection to wood formation, providing interesting targets for improving nitrogen-use efficiency and growth of aspen trees.

@article{derba-maceluch_glucuronoyl_2025,
	title = {Glucuronoyl {Esterase} {Expressed} in {Aspen} {Xylem} {Affects} γ-{Ester} {Linkages} {Between} {Lignin} and {Glucuronoxylan} {Reducing} {Recalcitrance} and {Accelerating} {Growth}},
	volume = {23},
	copyright = {© 2025 The Author(s). Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley \& Sons Ltd.},
	issn = {1467-7652},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/pbi.70301},
	doi = {10.1111/pbi.70301},
	abstract = {Wood is the most abundant renewable natural resource composed of different polysaccharides and lignin, but its utilisation is hampered by intermolecular linkages between these components forming lignin-carbohydrate complexes (LCCs) causing recalcitrance. The links between glucuronoxylan and the γ-C of lignin (γ-ester linkages) are thought to contribute to one-third of LCCs, but direct evidence for their natural occurrence and their role in recalcitrance has been scarce so far. To address these issues, Phanerochaete carnosa glucuronoyl esterase (PcGCE), hydrolysing γ-ester linkages, was expressed in cell walls of developing wood in hybrid aspen (Populus tremula L. × tremuloides Michx.). The enzyme reduced HSQC 2D NMR signals corresponding to the γ-esters and xylan in dioxane-extracted LCCs without altering glucuronoxylan content or structure. This increased acid solubility of lignin and decreased lignin content. Reduced wood recalcitrance was shown by increased sugar yields and glucose production rates (by approx. 20\%) in saccharification without pretreatment and increased xylan extractability by subcritical water (by approx. 70\%). Moreover, trees expressing PcGCE exhibited greater primary and secondary growth. Transcriptomics and metabolomics analyses in developing wood suggested that growth could have been induced by a higher transcription of SMR2 and RPOTmp, which was likely triggered by the secondary cell wall integrity signalling. The results provide evidence for the natural existence of LCC γ-esters and their significant contribution to lignocellulose recalcitrance. Furthermore, they show that reducing γ-ester linkages could increase plant productivity.},
	language = {en},
	number = {12},
	urldate = {2025-12-05},
	journal = {Plant Biotechnology Journal},
	author = {Derba-Maceluch, Marta and García Romañach, Laura and Hedenström, Mattias and Mitra, Madhusree and Donev, Evgeniy N. and Urbancsok, János and Yassin, Zakiya and Gandla, Madhavi L. and Sivan, Pramod and Šimura, Jan and Scheepers, Gerhard and Jönsson, Leif J. and Vilaplana, Francisco and Mellerowicz, Ewa J.},
	year = {2025},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/pbi.70301},
	keywords = {ce15, glucuronoxylan, glucuronoyl esterase, hardwood genetic engineering, lignin-carbohydrate complexes, lignocellulose, secondary cell wall},
	pages = {5417--5434},
}

Wood is the most abundant renewable natural resource composed of different polysaccharides and lignin, but its utilisation is hampered by intermolecular linkages between these components forming lignin-carbohydrate complexes (LCCs) causing recalcitrance. The links between glucuronoxylan and the γ-C of lignin (γ-ester linkages) are thought to contribute to one-third of LCCs, but direct evidence for their natural occurrence and their role in recalcitrance has been scarce so far. To address these issues, Phanerochaete carnosa glucuronoyl esterase (PcGCE), hydrolysing γ-ester linkages, was expressed in cell walls of developing wood in hybrid aspen (Populus tremula L. × tremuloides Michx.). The enzyme reduced HSQC 2D NMR signals corresponding to the γ-esters and xylan in dioxane-extracted LCCs without altering glucuronoxylan content or structure. This increased acid solubility of lignin and decreased lignin content. Reduced wood recalcitrance was shown by increased sugar yields and glucose production rates (by approx. 20%) in saccharification without pretreatment and increased xylan extractability by subcritical water (by approx. 70%). Moreover, trees expressing PcGCE exhibited greater primary and secondary growth. Transcriptomics and metabolomics analyses in developing wood suggested that growth could have been induced by a higher transcription of SMR2 and RPOTmp, which was likely triggered by the secondary cell wall integrity signalling. The results provide evidence for the natural existence of LCC γ-esters and their significant contribution to lignocellulose recalcitrance. Furthermore, they show that reducing γ-ester linkages could increase plant productivity.

@article{biswal_ectopic_2025,
	title = {Ectopic expression of pectate lyase \textit{{Ptxt}}{PL1}-27 in aspen affects leaf cuticle development},
	volume = {28},
	issn = {2589-0042},
	url = {https://www.sciencedirect.com/science/article/pii/S2589004225022242},
	doi = {10.1016/j.isci.2025.113963},
	abstract = {Cuticle - a hydrophobic barrier of cutin and waxes covering the outer cell wall surface of plants - enables survival in terrestrial habitats. However, it is not understood how the hydrophobic cuticle precursors travel through the homogalacturonan-rich hydrophilic cell wall. To elucidate the role of homogalacturonan in cuticle development, we disrupted its integrity by overexpressing a pectate lyase, PtxtPL1-27, in aspen. PtxtPL1-27 had pleiotropic effects on shoot development, including the reduction of cuticle thickness and changes in cutin and wax composition, but the expression of cutin biosynthetic genes was little affected. Despite a reduction in homogalacturonan content in the leaves, labeling with the homogalacturonan-specific antibody JIM5 in the outer epidermal cell wall layer increased and displayed an altered pattern. Moreover, the ultrastructure of cell walls was changed concomitant with lipid accumulation. We propose that the disruption of homogalacturonan integrity affected the cutinsome-dependent transport and polymerization of cutin monomers in the cell wall.},
	number = {12},
	urldate = {2025-11-28},
	journal = {iScience},
	author = {Biswal, Ajaya K. and Banasiak, Alicja and Fernández-Moreno, Josefina-Patricia and Mitra, Madhusree and Harholt, Jesper and Derba-Maceluch, Marta and Majda, Mateusz and Kushwah, Sunita and Kumar, Vikash and Abreu, Ilka and Sivan, Pramod and Pattathil, Sivakumar and Immerzeel, Peter and Gorzsás, András and Moritz, Thomas and Hahn, Michael G. and Scheller, Henrik Vibe and Aharoni, Asaph and Mellerowicz, Ewa J.},
	month = dec,
	year = {2025},
	keywords = {Plant Biology, Plant anatomy, Plant development, Plant physiology},
	pages = {113963},
}

Cuticle - a hydrophobic barrier of cutin and waxes covering the outer cell wall surface of plants - enables survival in terrestrial habitats. However, it is not understood how the hydrophobic cuticle precursors travel through the homogalacturonan-rich hydrophilic cell wall. To elucidate the role of homogalacturonan in cuticle development, we disrupted its integrity by overexpressing a pectate lyase, PtxtPL1-27, in aspen. PtxtPL1-27 had pleiotropic effects on shoot development, including the reduction of cuticle thickness and changes in cutin and wax composition, but the expression of cutin biosynthetic genes was little affected. Despite a reduction in homogalacturonan content in the leaves, labeling with the homogalacturonan-specific antibody JIM5 in the outer epidermal cell wall layer increased and displayed an altered pattern. Moreover, the ultrastructure of cell walls was changed concomitant with lipid accumulation. We propose that the disruption of homogalacturonan integrity affected the cutinsome-dependent transport and polymerization of cutin monomers in the cell wall.

@article{jiao_integrating_2025,
	title = {Integrating parental breeding value, genetic gain, and gamete contribution for elite family selection in {Platycladus} orientalis},
	volume = {37},
	issn = {1993-0607},
	url = {https://doi.org/10.1007/s11676-025-01943-7},
	doi = {10.1007/s11676-025-01943-7},
	abstract = {Platycladus orientalis (L.) Franco seed orchards play an important role in sustainable forestry in China but balancing genetic gain and genetic diversity remains a significant challenge. Two key factors influence the success of seed orchards: parental breeding value and gamete contribution, as they determine both the genetic gain and diversity of the seed crops produced. This study aimed to optimize breeding strategies by analyzing parental breeding value, gamete contribution, and genetic gain across two growth periods (89 families in 2008 and 52 families in 2021). We evaluated height, diameter at breast height, and stem volume of progeny in a primary seed orchard, uncovering significant genetic variation among families. Interestingly, no correlation was found between growth traits and gamete contribution, indicating their independence. Using comprehensive scoring and PCA-biplot analysis, we consistently identified several elite families with superior growth performance in both years. We propose an optimal breeding strategy that combines 30\% selective harvesting and 50\% selective thinning to effectively balance genetic gain and genetic diversity, addressing a critical goal in tree improvement programs. The selected families and optimized strategy provide a scalable framework not only for P. orientalis but also for other conifer species globally, enhancing both productivity and genetic diversity in afforestation efforts.},
	language = {en},
	number = {1},
	urldate = {2025-11-28},
	journal = {Journal of Forestry Research},
	author = {Jiao, Si-Qian and Li, Meiyu and Li, Zhi-Chao and Bao, Yu-Tao and Zhang, Hui-Jin and Yang, Xiao-Lei and El-Kassaby, Yousry Aly and Cheng, Shi-Ping and Mao, Jian-Feng},
	month = nov,
	year = {2025},
	keywords = {Breeding strategy, Comprehensive evaluation, Genetic gain, Platycladus orientalis, Progeny test},
	pages = {5},
}

Platycladus orientalis (L.) Franco seed orchards play an important role in sustainable forestry in China but balancing genetic gain and genetic diversity remains a significant challenge. Two key factors influence the success of seed orchards: parental breeding value and gamete contribution, as they determine both the genetic gain and diversity of the seed crops produced. This study aimed to optimize breeding strategies by analyzing parental breeding value, gamete contribution, and genetic gain across two growth periods (89 families in 2008 and 52 families in 2021). We evaluated height, diameter at breast height, and stem volume of progeny in a primary seed orchard, uncovering significant genetic variation among families. Interestingly, no correlation was found between growth traits and gamete contribution, indicating their independence. Using comprehensive scoring and PCA-biplot analysis, we consistently identified several elite families with superior growth performance in both years. We propose an optimal breeding strategy that combines 30% selective harvesting and 50% selective thinning to effectively balance genetic gain and genetic diversity, addressing a critical goal in tree improvement programs. The selected families and optimized strategy provide a scalable framework not only for P. orientalis but also for other conifer species globally, enhancing both productivity and genetic diversity in afforestation efforts.

@article{wang_genetic_2025,
	title = {Genetic control of seasonal meristem arrest in trees},
	volume = {122},
	url = {https://www.pnas.org/doi/10.1073/pnas.2505641122},
	doi = {10.1073/pnas.2505641122},
	abstract = {Perennial plants, such as trees native to temperate and boreal regions, exhibit meristems that undergo annual cycles of activity and rest to synchronize their growth cycles with seasonal changes, ensuring survival under harsh winter conditions. The arrest of shoot meristem growth, known as growth cessation, is a critical initial step for trees to enter dormancy. This process is triggered by a combination of endogenous and exogenous signals, yet the molecular mechanisms and signaling pathways underlying growth cessation remain poorly understood. In this study, we demonstrate that Populus orthologs of APETALA2-like transcription factors (AP2Ls), the primary regulators of global proliferative arrest (GPA) in Arabidopsis, play a crucial role in the regulation of seasonal growth cessation in hybrid aspen trees. In particular, AP2Ls act as important activators of the expression of FLOWERING LOCUS T2 (FT2), a key gene for short-day-induced growth cessation. This contrasts with the established role of AP2Ls as repressors of FT in annual plants. Yet, the pathway itself is conserved with the pathway regulating GPA in annual plants, a completely different process during the plant life cycle. Our research highlights both the conserved roles and functional diversities of AP2Ls in a more general balancing of meristem proliferation and arrest in perennial plants, providing insights into the evolutionary adaptation of growth regulation mechanisms across plant species.},
	number = {48},
	urldate = {2025-11-28},
	journal = {Proceedings of the National Academy of Sciences},
	author = {Wang, Jun and Liao, Xiaoli and Wu, Zhihao and Sane, Shashank and Han, Shaopeng and Chen, Qihui and Shi, Xueping and Dai, Xiaokang and Klintenäs, Maria and Nilsson, Ove and Ding, Jihua},
	month = dec,
	year = {2025},
	note = {Publisher: Proceedings of the National Academy of Sciences},
	pages = {e2505641122},
}

Perennial plants, such as trees native to temperate and boreal regions, exhibit meristems that undergo annual cycles of activity and rest to synchronize their growth cycles with seasonal changes, ensuring survival under harsh winter conditions. The arrest of shoot meristem growth, known as growth cessation, is a critical initial step for trees to enter dormancy. This process is triggered by a combination of endogenous and exogenous signals, yet the molecular mechanisms and signaling pathways underlying growth cessation remain poorly understood. In this study, we demonstrate that Populus orthologs of APETALA2-like transcription factors (AP2Ls), the primary regulators of global proliferative arrest (GPA) in Arabidopsis, play a crucial role in the regulation of seasonal growth cessation in hybrid aspen trees. In particular, AP2Ls act as important activators of the expression of FLOWERING LOCUS T2 (FT2), a key gene for short-day-induced growth cessation. This contrasts with the established role of AP2Ls as repressors of FT in annual plants. Yet, the pathway itself is conserved with the pathway regulating GPA in annual plants, a completely different process during the plant life cycle. Our research highlights both the conserved roles and functional diversities of AP2Ls in a more general balancing of meristem proliferation and arrest in perennial plants, providing insights into the evolutionary adaptation of growth regulation mechanisms across plant species.