CsCAD Genes Mediate Lignin Deposition to Regulate Petiole Angle Formation in Cucumber

doi:10.13560/j.cnki.biotech.bull.1985.2026-0106

Abstract

Abstract:

Objective To characterize the CAD gene family in cucumber (Cucumis sativus L.) and explore its potential roles in regulating petiole angle formation, providing candidate genes for improving plant architecture. Method Based on the cucumber reference genome CLv4.0, CAD family members were identified using domain-based and homology-based approaches. Their chromosomal distribution, physicochemical properties, gene structures, conserved motifs, phylogenetic relationships, promoter cis-acting elements, and synteny were systematically analyzed. Candidate genes were further screened using multi-tissue transcriptome data. Expression patterns were analyzed by RT-qPCR in the adaxial petiole base and shoot-tip leaves of cucumber materials with contrasting petiole angles. Lignin content was measured, and subcellular localization of selected proteins was determined. Result A total of 22 CAD genes were identified in the cucumber genome and unevenly distributed across seven chromosomes, with three pairs of tandem duplications detected. Phylogenetic analysis classified these genes into four subgroups, among which subgroup II showed significant expansion. Promoter analysis revealed that CsCAD genes were enriched in hormone-responsive and stress-related cis-elements. Tissue expression analysis indicated that several CsCAD genes were highly expressed in mechanically relevant tissues. Further analysis showed that CsCAD13 and related genes were highly expressed in the adaxial petiole base of small-angle materials, whereas CsCAD19 and CsCAD14 exhibited higher expression in shoot-tip leaves of large-angle materials. Lignin content was significantly higher in the adaxial petiole base of small-angle materials. Subcellular localization revealed distinct intracellular distribution patterns among CsCAD proteins. Conclusion The cucumber CAD gene family exhibits both conservation and expansion with functional divergence. Some CsCAD genes may regulate petiole angle formation by modulating lignin accumulation in the adaxial petiole base or affecting shoot-tip tissue development, providing potential targets for cucumber plant architecture improvement. This study is the first to link the CAD gene family with petiole angle, a key trait of plant architecture in cucumber.

Key words: Cucumissativus L., petiole angle, CAD gene family, adaxial petiole base, lignin biosynthesis, tissue-specific expression, plant architecture, genome-wide identification

QIN Shao-min, MIAO Han, DONG Shao-yun, GUAN Jian-tao, GU Xing-fang, LI Sen, LIU Xiao-ping, ZHANG Sheng-ping. CsCAD Genes Mediate Lignin Deposition to Regulate Petiole Angle Formation in Cucumber[J]. Biotechnology Bulletin, 2026, 42(9): 137-146.

Figures/Tables 10

Table 1 Petiole angle measurements at nodes 15-17 in different cucumber materials

材料 Material	节位15 Node15 （°）	节位16 Node16 （°）	节位17 Node17 （°）	平均值 Mean （°）
R369	25.67 ± 0.67	26.00 ± 0.58	26.33 ± 0.67	26.00 ± 0.33
R506	43.67 ± 1.76	44.33 ± 0.88	43.67 ± 1.76	43.89 ± 0.67
R116	63.00 ± 3.46	61.33 ± 0.88	61.67 ± 3.33	62.00 ± 1.04
R60	55.00 ± 1.73	55.33 ± 2.03	54.67 ± 0.33	55.00 ± 0.33

Fig. 1 Distribution diagram of plant sample collection sites

Table 2 Comparison of lignin content in adaxial petiole base and shoot-tip leaves among cucumber materials with different petiole angles

材料 Sample	取样部位 Sampling part	木质素含量 Lignin content （mg/g）	百分含量 Percentage （%）
R116	近轴叶柄基部	91.87 ± 0.50	9.19 ± 0.04
	生长点叶片	44.41 ± 4.17	4.44 ± 0.37
R60	近轴叶柄基部	96.10 ± 1.51	9.61 ± 0.15
	生长点叶片	73.53 ± 1.32	7.35 ± 0.13
R369	近轴叶柄基部	145.89 ± 1.31	14.59 ± 0.13
	生长点叶片	103.23 ± 0.87	10.32 ± 0.09
R506	近轴叶柄基部	140.36 ± 1.53	14.04 ± 0.15
	生长点叶片	67.70 ± 0.44	6.77 ± 0.04

Fig. 2 Chromosomal distribution of the CsCAD gene family in cucumber

Fig. 3 Gene structure analysis of CsCADA: Phylogenetic tree and conserved motifs. B: Conserved domains. C: Gene structures. D: Cis-acting elements

Fig. 4 Phylogenetic analysis of the CAD gene family

Fig. 5 Collinearity analysis of CsCAD genes among cucumber, Arabidopsis thaliana, and Cucumis melo

Fig. 6 Expression profiles of CsCAD genes across different tissues in cucumber

Fig. 7 Expression analysis of candidate CsCAD genes in adaxial petiole base and shoot-tip leaves of cucumber materials with different petiole anglesHorizontal lines and symbols above the bars indicate the significance of differences between groups. ns indicates no significant difference (P>0.05); asterisks indicate significant differences: * P<0.05, ** P<0.01, *** P<0.001, and **** P<0.000 1

Fig. 8 Subcellular localization of CsCAD13, CsCAD14 and CsCAD19 proteins

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