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Carbon monoxide (CO) has been reported to be participated in adventitious rooting. However, knowledge about the interrelationship between CO and phytohormones during rooting is obscure. The molecular mechanism of CO-induced rooting is currently unclear.The roles of CO in adventitious rooting in Cucumis sativus L. at the transcriptional level were investigated. The results show that 10 μM hematin (a CO donor) has a significant positive effect on adventitious rooting in cucumber. A total of 1792 differentially expressed genes (DEGs; 1103 up-regulated and 689 down-regulated) were identified in hematin treatment by RNA sequencing analysis. There were 37, 18 and 19 DEGs significantly enriched in plant hormone signal transduction, sucrose and starch metabolism, and phenylalanine metabolism, respectively. Both transcriptome and real-time quantitative PCR results showed that the expressions of AUX22D, IAA6, SAUR21, SAUR24, GH3.5, CYCD3-3, TIFY10a, TIFY10A and TIF9 promoted the accumulation of IAA, BR, JA and SA in plant hormone signal transduction. The up-regulation of HK3, TPPF, otsB, TPS7, TPS9 and the down-regulation of AGPS1, AGPS3 increased the content of starch and total sugar by mediating the activity of some critical enzymes, including HK, TPS, TPP and AGP. PER47, PER61, PER24, PER66, PER4 and CCR2 increased the lignin content.Our results suggest that CO could promote the accumulation of plant hormones, starch, sugar and lignin during adventitious rooting by regulating the expression of some related genes, including AUX22D, IAA6, SAUR21, SAUR24, GH3.5, CYCD3-3, TIFY10a, TIFY10A, TIF9 HK3, otsB, TPS7, TPS9, AGPS1, AGPS3, PER47, PER61, PER24, PER66, PER4, and CCR2. Thus, we provides an interesting candidate gene list for further studies on the molecular mechanisms of adventitious rooting.

The calmodulin-binding transcription activator (CAMTA), as one of the most distinctive families of transcription factors, plays an important role in plant growth and development and in the stress response. However, it is currently unknown whether CAMTA exists in cucumbers and what its function is. In this study, we first identified four CAMTA genes in the cucumber genome using a genome-wide search method. Subsequently, we analyzed their physical and chemical properties, gene structure, protein domains, and phylogenetic relationships. The results show that the structure of CsCAMTAs is similar to that of other plants, and a phylogenetic analysis divides them into three groups. The analysis of cis-acting elements shows that most CsCAMTAs contain a variety of hormones and stress-related elements. The RT-PCR analysis shows that CsCAMTAs have different expression levels in different tissues and can be induced by IAA, ABA, MeJA, NaCl, and PEG. Finally, we analyzed the expression pattern of CsCAMTAs’ alternative spliceosomes under salt and drought stress. The results show that the expression levels of the different spliceosomes are affected by the type of stress and the duration of stress. These data indicate that CsCAMTAs participate in growth and development and in the stress response in cucumbers, a finding which lays the foundation for future CsCAMTAs’ functional research.