Abstract
Cyclins, a prominent class of cell division regulators, play an extremely important role in plant growth and development. D-type cyclins (CYCDs) are the rate-limiting components of the G1 phase. In plants, studies of CYCDs are mainly concerned with herbaceous plants, yet little information is available about these genes in perennial woody plants, especially ornamental plants. Here, twelve Prunus mume CYCD (PmCYCDs) genes are identified and characterized. The PmCYCDs were named on the basis of orthologues in Arabidopsis thaliana and Oryza sativa. Gene structure and conserved domains of each subgroup CYCDs was similar to that of their orthologues in A. thaliana and O. sativa. However, PmCYCDs exhibited different tissue-specific expression patterns in root, stem, leaf, bud, and fruit organs. The results of qRT-PCR showed that all PmCYCDs, except PmCYCD5;2 and PmCYCD7;1, were primarily highly expressed in leaf buds, shoots, and stems. In addition, the transcript levels of PmCYCD genes were analyzed in roots under different treatments, including exogenous applications of NAA, 6-BA, GA3, ABA, and sucrose. Interestingly, although PmCYCDs were induced by sucrose, the extent of gene induction among PmCYCD subgroups varied. The induction of PmCYCD1;2 by hormones depended on the presence of sucrose. PmCYCD3;1 was stimulated by NAA, and induction was strengthened when sugar and hormones were applied together. Taken together, our study demonstrates that PmCYCDs are functional in plant stem development and provides a basis for selecting members of the cyclin gene family as candidate genes for ornamental plant breeding.
Highlights
The organs of higher plants are developing constantly throughout their life cycle, relying on the flexible control of cell division and cell proliferation
P. mume, and 10 D-type cyclin from A. thaliana were used to perform a BLASTP search against P. mume cyclin protein sequences obtained from the HMMER search
CYCD proteins of P. mume were divided into six subfamilies that were assigned to different subgroups of homologous genes reported in Arabidopsis and rice: CYCD1, CYCD2/CYCD4, CYCD3, CYCD5, CYCD6, and CYCD7 (Table S2): There are two each of the CYCD1, CYCD2/D4, CYCD5, and CYCD6-type cyclins and one CYCD7-type cyclin, and three CYCD3-type cyclins
Summary
The organs of higher plants are developing constantly throughout their life cycle, relying on the flexible control of cell division and cell proliferation. G1/S transition in mammals and plants are functionally conserved and are characterized as D-type cyclin (CYCD)/retinoblastoma (Rb) pathways [3]. CYCD and a cyclin-dependent kinase (CDK) form a CYCD-CDK complex that binds to the Rb protein through the LxCxE (x represents any amino acid) motif of CYCD to activate the phosphorylation of the Rb protein [4,5]. Since the first plant CYCD was discovered in Arabidopsis thaliana [7], more CYCDs have been identified from various organisms. 10 genes encoding CYCDs have been identified in A. thaliana, which are divided into seven sub-families (CYCD1–CYCD7).
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