Tree Genetics and Molecular Breeding 2024, Vol.14, No.5, 218-228 http://genbreedpublisher.com/index.php/tgmb 221 winter to early spring can lead to earlier initiation of cambial activity, extending the growth period but also increasing the risk of frost damage due to decreased cold tolerance post-reactivation (Begum et al., 2013). Additionally, the immediate environment of cambial cells, including weather and nutritional factors, continuously varies, influencing wood formation and the variability in wood properties (Downes et al., 2009). 4.2 Molecular response mechanisms to abiotic stress Cambium stem cells employ various molecular mechanisms to respond to abiotic stress. For instance, temperature-induced changes in the stability of microtubules are crucial for the reactivation of cambial cells and subsequent xylem differentiation (Begum et al., 2013). Hormones, peptides, and mechanical cues are also believed to orchestrate the response of cambial activity to environmental factors, although the exact mechanisms remain to be fully uncovered (Fischer et al., 2019). In Populus, the peptide PtrCLE20 has been identified as a repressor of vascular cambium activity, suggesting a role in modulating growth in response to environmental cues (Zhu et al., 2019). Furthermore, conserved gene-regulatory networks involving stress-response transcription factors, such as ERF-1, integrate environmental sensing with cambium-driven growth, highlighting the complex interplay between environmental signals and cambial activity (Chiatante et al., 2018; Hoang et al., 2020). 4.3 Molecular response mechanisms to biotic stress In response to biotic stress, such as pathogen attacks, cambium stem cells activate specific molecular pathways to mitigate damage and maintain growth. The identification of receptor-like kinases, such as REDUCED IN LATERAL GROWTH1 (RUL1) and MORE LATERAL GROWTH1 (MOL1), which act as opposing regulators of cambium activity, underscores the importance of cell-to-cell communication in the cambium's response to biotic stress (Agustí et al., 2011). These signaling components help coordinate the cambium's activity, ensuring the production of secondary phloem and xylem even under stress conditions. Additionally, the dynamic nature of cambial stem cell activity, influenced by mobile signals and intercellular communication, plays a critical role in the plant's ability to adapt to biotic stress (Bhalerao and Fischer, 2017; Fischer et al., 2019). 4.4 Integration of stress signals in cambium regulation The integration of stress signals in cambium regulation involves a complex network of molecular interactions. Phytohormones, transcription factors, and peptide-receptor modules are key players in this process. Recent studies have highlighted the roles of mobile transcription factors and intercellular signaling in the regulation of cambium activity, emphasizing the crosstalk between different regulatory pathways (Turley and Etchells, 2021). The environment of cambial cells, including fluxes in phytohormones, carbohydrates, and physical factors, influences gene expression and enzyme kinetics, thereby modulating cambial activity in response to stress (Savidge, 2001). Understanding these integrative mechanisms is crucial for developing strategies to enhance tree growth and resilience under changing environmental conditions. 5 Collaborative Regulation Networks of Cambium, Xylem, and Phloem Development 5.1 Gene networks involved in cambium development The development and activity of the vascular cambium are regulated by complex gene networks. Key transcription factors such as WUSCHEL-RELATED HOMEOBOX 4 (WOX4) and KNOTTED-like from Arabidopsis thaliana 1 (KNAT1) play crucial roles in cambium development. Mutations in these genes can lead to significant changes in cambial activity, highlighting their importance in the regulatory network (Zhang et al., 2019). Additionally, MADS-box genes like VCM1 and VCM2 have been identified to modulate auxin homeostasis, which is essential for cambium proliferation and secondary growth in Populus (Zheng et al., 2020). The interaction between these genes and hormonal pathways, such as auxin and gibberellin signaling, further underscores the complexity of the gene networks involved in cambium development (Ben-Targem et al., 2021). 5.2 Interactions between cambium, xylem, and phloem gene networks The gene networks regulating cambium activity are intricately linked with those controlling xylem and phloem development. For instance, the transcription factors WOX4 and SHORT VEGETATIVE PHASE (SVP) have dual roles in cambial cell proliferation and xylem differentiation (Zhang et al., 2019). Hormonal signaling pathways, including auxin and gibberellin, also play a pivotal role in coordinating the development of these tissues. Auxin
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