Plant Gene and Trait 2024, Vol.15, No.1, 8-14 http://genbreedpublisher.com/index.php/pgt 12 Figure 4 Expression analysis of cucumber SBP genes in different tissues Image caption: 1: Roots (4 week seedlings); 2: Hypocotyls (4 week seedlings); 3: Cotyledons (4 week seedlings); 4: Euphylla (4 week seedlings); 5: Root; 6: Stem; 7: Spire; 8: Petiole (Spire); 9: Old leaves; 10: Petiole (Old leaf); 11: Tendril; 12: Female flowers; 13: Male flower bud; 14: Male flowers; 15: Unfertilized ovary; 16: Pericarp (Unfertilized ovary); 17: Pulp (Unfertilized ovary); 18: Pericarp (One week after pollination); 19: Pulp (One week after pollination); 20: Pericarp (Two weeks after pollination); 21: Pulp (Two weeks after pollination); 22: Pericarp (Three weeks after pollination); 23: Pulp (Three weeks after pollination) 3 Discussion In this study, we identified and analyzed the cucumber SBP gene family members at the whole-genome level using bioinformatics tools, including their chromosome positions, phylogenetic relationships, conserved motifs, gene structures, and expression patterns. We identified 15 cucumber SBP genes in this study, which is similar to the number of SBP members in Arabidopsis (16 members), despite the cucumber genome (367 Mb) being approximately three times larger than the Arabidopsis genome (125 Mb) (Huang et al., 2009). Whole-genome duplication (WGD) is common in angiosperms and can result in gene duplication and the potential for new gene functions. Studies have shown that Arabidopsis experienced three rounds of WGD, with the most recent two rounds (α and β) playing important roles in the rapid expansion of genes, following a whole-genome triplication (γ) event in the common ancestor of flowering plants (Cannon et al., 2004). However, cucumber lacks the two most recent WGD events (Huang et al., 2009), which may explain why the number of SBP genes identified in this study is not higher than that in Arabidopsis. Phylogenetic analysis revealed that cucumber and Arabidopsis SBP members could be classified into six classes (Figure 4), with Class II lacking cucumber SBP members, suggesting that the genes in Class II of Arabidopsis may have undergone independent evolutionary events. Typically, genes of the same type have similar gene structures and motif compositions. Transcription factor domains and motifs are often related to protein interactions, transcriptional activity, and DNA binding (Liu et al., 1999). Eight cucumber members contained the conserved motif Motif-5 (ALSLLS), which corresponds to the target sequence of mRNA156 in Arabidopsis (Rhoades et al., 2002). Expression analysis showed that CsSBP9 was expressed in all tissues, and its Arabidopsis homolog SPL14 (AT1G20980) was expressed in cotyledons, leaves, roots, and floral organs. CsSBP14 was mainly expressed in reproductive organs, particularly in fruit flesh and skin, and its Arabidopsis homolog SPL8 was also mainly expressed in inflorescences and siliques. This suggested that these genes have similar biological functions in different species (Stone et al., 2005) and may have undergone convergent evolution (Qian and Zhang, 2014). Our bioinformatics analysis of the cucumber SBP gene family provides a theoretical basis for future studies on the functions of SBP transcription factors. 4 Materials and Methods 4.1 Identification of SBPgenes in cucumber In this study, the cucumber SBP family genes were identified using a bidirectional BLAST approach. Firstly, the Arabidopsis SBP protein sequences were aligned to the cucumber genome using TBtools software (e-value, 1e-5)
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