Plant Gene and Trait 2024, Vol.15, No.2, 97-107 http://genbreedpublisher.com/index.php/pgt 98 2 Overview of Asexual Reproduction in Plants 2.1 Mechanisms of asexual reproduction in angiosperms Asexual reproduction in angiosperms involves various mechanisms that allow plants to reproduce without the fusion of gametes. This process can occur through vegetative propagation, where new plants grow from parts of the parent plant such as stems, roots, or leaves (Hewitt, 2020). Key genes and protein domains play a significant role in these processes. For instance, the expansion of certain protein domains in Eucalyptus has been linked to tissue-specific expression and subfunctionalization, which are crucial for the specialization of reproduction and interactions with the environment (Kersting et al., 2015). Additionally, the overexpression of specific genes like FLOWERING LOCUS T (FT) can induce early flowering, which is a form of asexual reproduction that accelerates breeding and genetic studies (Klocko et al., 2016). 2.2 Advantages of asexual reproduction in forestry Asexual reproduction offers several advantages in forestry, particularly for species like Eucalyptus that are vital for industrial purposes. One significant benefit is the ability to produce genetically identical offspring, ensuring uniformity in desirable traits such as growth rate, wood quality, and resistance to pests and diseases (Finkeldey and Hattemer, 2007). This uniformity is crucial for maintaining the consistency and quality of forestry products. Moreover, asexual reproduction can significantly reduce the time required for breeding programs. For example, the overexpression of FT genes in Eucalyptus can lead to precocious flowering, thereby speeding up the breeding cycle and enabling faster genetic improvements (Klocko et al., 2016). This method also allows for the rapid propagation of superior genotypes, ensuring that the best traits are perpetuated in subsequent generations. 2.3 Common methods of asexual reproduction inEucalyptus Eucalyptus species employ several common methods of asexual reproduction, including vegetative propagation techniques such as cuttings, grafting, and tissue culture. These methods are widely used to produce clones of elite trees with desirable traits (Assis, 2011). The genetic basis of these methods is often linked to the expansion and modulation of specific protein domains that facilitate tissue-specific expression and functional specialization (Kersting et al., 2015). Additionally, genetic engineering approaches, such as the overexpression of FT genes, have been developed to induce early flowering and enhance reproductive efficiency in Eucalyptus (Klocko et al., 2016). These methods not only improve the speed and efficiency of breeding programs but also ensure the propagation of high-quality, uniform plant material for forestry applications. 3 Key Genes Involved in Asexual Reproduction 3.1 Identification of key genes inEucalyptus The identification of key genes involved in asexual reproduction in Eucalyptus has been a focal point of recent research. One significant study utilized transcriptome analysis to identify differentially expressed genes (DEGs) during the somatic embryogenesis (SE) process in Eucalyptus species. The study by Xiao et al. (2020) identified several genes, including somatic embryogenesis receptor kinase, ethylene, auxin, ribosomal protein, zinc finger protein, heat shock protein, histone, cell wall-related, and transcription factor genes, which are crucial for the dedifferentiation process necessary for SE. Another study focused on the LEAFY (LFY) orthologue, ELFY, in Eucalyptus, demonstrating that its disruption via CRISPR-Cas9 led to significant alterations in floral development, indicating its critical role in reproductive processes (Elorriaga et al., 2021). Additionally, the Eucalyptus cinnamoyl-CoA reductase1 (EgCCR1) gene was identified as a key player in lignin biosynthesis, which is essential for secondary cell wall formation and overall plant structure, indirectly influencing asexual reproduction capabilities (Plasencia et al., 2016). 3.2 Functional roles of these genes in asexual reproductive processes The functional roles of these identified genes are diverse and critical for the asexual reproductive processes in Eucalyptus. The somatic embryogenesis receptor kinase and other DEGs identified in the transcriptome analysis are involved in the dedifferentiation of plant cells, a crucial step for SE, which allows for the vegetative propagation of Eucalyptus (Xiao et al., 2020). The ELFY gene, when disrupted, leads to sterile indeterminate inflorescences, indicating its role in controlling floral organ identity and development, which is essential for
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