Medicago species A2-type cyclin is auxin regulated and involved in meristem formation but dispensable for endoreduplication-associated developmental programs

• Published in: Plant physiology (Bethesda) 2003-03, Vol.131 (3), p.1091-1103
• Main Authors: Roudier, F, Fedorova, E, Lebris, M, Lecomte, P, Gyorgyey, J, Vaubert, D, Horvath, G, Abad, P, Kondorosi, A, Kondorosi, E
• Format: Article
• Language: English
• Subjects: Alfalfa; Animals; antisense RNA; apical meristems; Auxins; Base Sequence; Cell cycle; Cell Differentiation; Cell Differentiation - genetics; Cell Differentiation - physiology; Cyclin A; Cyclin A - drug effects; Cyclin A - genetics; Cyclin A - metabolism; cyclin A2; Cyclins; Development and Hormone Action; forage legumes; gene expression regulation; Gene Expression Regulation, Developmental; Gene Expression Regulation, Developmental - drug effects; Gene Expression Regulation, Plant; Gene Expression Regulation, Plant - drug effects; gene overexpression; Giant cells; Glucuronidase; Glucuronidase - genetics; Glucuronidase - metabolism; Indoleacetic Acids; Indoleacetic Acids - pharmacology; Life Sciences; Medicago; Medicago - genetics; Medicago - growth & development; Medicago - metabolism; Medicago sativa; Meloidogyne incognita; Meristem; Meristem - genetics; Meristem - growth & development; Meristem - metabolism; Meristems; Mitosis; Mitosis - genetics; Mitosis - physiology; Molecular Sequence Data; Nematoda; Nematoda - growth & development; Nod factor; Nodules; nucleotide sequences; plant anatomy; Plant Proteins; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Roots; Plant Roots - genetics; Plant Roots - growth & development; Plant Roots - metabolism; Plant Tumors; Plant Tumors - genetics; Plant Tumors - parasitology; Plants; Plants, Genetically Modified; protein synthesis; Recombinant Fusion Proteins; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Root development; root galls; root meristems; root nodules; root systems; root-knot nematodes; Seeds; Seeds - genetics; Seeds - growth & development; symbiosis; Transgenic plants; Vegetal Biology
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.102.011122

Phytohormones as well as temporal and spatial regulation of the cell cycle play a key role in plant development. Here, we investigated the function and regulation of an alfalfa (Medicago sativa) A2-type cyclin in three distinct root developmental programs: in primary and secondary root development, nodule development, and nematode-elicited gall formation. Using transgenic plants carrying the Medsa;cycA2;2 promoter-β-glucuronidase gene fusion, in combination with other techniques, cycA2;2 expression was localized in meristems and proliferating cells in the lateral root and nodule primordia. Rapid induction of cycA2;2 by Nod factors demonstrated that this gene is implicated in cell cycle activation of differentiated cells developing to nodule primordia. Surprisingly, cycA2;2 was repressed in the endoreduplicating, division-arrested cells both during nodule development and formation of giant cells in nematode-induced galls, indicating that CycA2;2 was dispensable for S-phase in endoreduplication cycles. Overexpression of cycA2;2 in transgenic plants corresponded to wild type protein levels and had no apparent phenotype. In contrast, antisense expression of cycA2;2 halted regeneration of somatic embryos, suggesting a role for CycA2;2 in the formation or activity of apical meristems. Expression of cycA2;2 was up-regulated by auxins, as expected from the presence of auxin response elements in the promoter. Moreover, auxin also affected the spatial expression pattern of this cyclin by shifting the cycA2;2 expression from the phloem to the xylem poles.