ABSTRACT
Tendrils are filamentous plant organs that coil on contact with an object, thereby providing mechanical support for climbing to reach more sunlight. Plant tendrils are considered to be modified structure of leaves, stems, or inflorescence, but the origin of cucurbit tendrils is still argued because of the complexity in the axillary organ patterning. We carried out morphological and genetic analyses of the Chiba Tendril-Less (ctl) melon (Cucumis melo) mutant, and found strong evidence that the melon tendril is a modified organ derived from a stem-leaf complex of a lateral shoot. Heterozygous (CTL/ctl) plants showed traits intermediate between tendril and shoot, and ontogenies of wild-type tendrils and mutant modified shoots coincided. We identified the CTL locus in a 200-kb region in melon linkage group IX. A single base deletion in a melon TCP transcription factor gene (CmTCP1) was detected in the mutant ctl sequence, and the expression of CmTCP1 was specifically high in wild-type tendrils. Phylogenetic analysis demonstrated the novelty of the CmTCP1 protein and the unique molecular evolution of its orthologs in the Cucurbitaceae. Our results move us closer to answering the long-standing question of which organ was modified to become the cucurbit tendril, and suggest a novel function of the TCP transcription factor in plant development.
Subject(s)
Cucumis melo/genetics , Plant Proteins/genetics , Transcription Factors/genetics , Amino Acid Sequence , Cucumis melo/growth & development , Cucumis melo/metabolism , Mutation , Phylogeny , Plant Leaves/genetics , Plant Leaves/growth & development , Plant Proteins/chemistry , Plant Proteins/metabolism , Plant Stems/genetics , Plant Stems/growth & development , Sequence Alignment , Transcription Factors/chemistry , Transcription Factors/metabolismABSTRACT
As the fruits of loquat (Eriobotrya japonica, 2n = 2x = 34) carry large seeds, the breeding of seedless loquat has long been a goal. The recent creation of triploid cultivars (2n = 3x = 51) and the application of gibberellins allow commercial production of seedless loquat, but the possibility of seed formation in triploid loquats has not been carefully investigated. Through crossing experiments and cytological observations of meiosis and pollen tube growth, we found that the triploid line 3N-N28 was essentially self-sterile, but developed seeds on pollination with pollen from diploid cultivars at rates of up to 5.5%. Almost half of the seedlings survived to 5 months, and carried diploid (2n = 34), tetraploid (2n = 68), or aneuploid chromosome numbers. Our results suggest that triploid loquat cultivars might retain the risk of seed formation. Protection from pollination by diploid cultivars or the development of new triploid cultivars will be necessary to ensure the production of seedless loquat fruits.
ABSTRACT
The temperature dependence of seed germination and seedling growth was analyzed in Dioscorea tokoro, an East Asian summer-green perennial. Seeds were able to germinate fully only at 11-20 degrees C. At around 17-20 degrees C the first leaf petiole of the seedling elongated and quickly set the first leaf blade at a position enabling photosynthesis. At temperatures higher than 20 degrees C petiole elongation was retarded, and seedlings formed a rhizome and established as a perennial. The rhizome size increased with temperature up to 29 degrees C. Thus, during growth immediately after germination, temperature appears to be a key factor in determining whether the plant establishes as a perennial or grows rapidly without rhizome thickening.
