Journal
AMERICAN JOURNAL OF BOTANY
Volume 104, Issue 2, Pages 233-240Publisher
WILEY
DOI: 10.3732/ajb.1600303
Keywords
Gesneriaceae; groove meristem; indeterminate growth; KNOX gene; Monophyllaea; phyllomorph; shoot apical meristem
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Funding
- Monbusho International Scientific Research Program [25113002]
- Scientific Research on Innovation Areas of the Ministry of Education, Science, and Culture, Japan [15K21758]
- Precursory Research for Embryonic Science and Technology (PRESTO) program, Japan Science and Technology Corporation, Japan
- Grants-in-Aid for Scientific Research [15K21758, 25113002] Funding Source: KAKEN
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PREMISE OF THE STUDY: The aboveground part of one-leaf plants (Gesneriaceae) consists of a unique shoot-like unit called a phyllomorph, which is composed of a growing lamina and one petiolode (a stem-and petiole-like organ). The phyllomorph has three meristems: a basal meristem (BM; involved in lamina growth), a petiolode meristem (PM; required for midrib and petiolode growth), and a groove meristem (GM; contributes to inflorescence and new phyllomorph development). Although the GM has a tunica-corpus structure like a conventional shoot apical meristem (SAM), the vegetative GM of a one-leaf plant does not form any organ primordia and has been considered a defective or suppressed SAM. In this study, we evaluated the nature of the three meristems to reconsider their roles in phyllomorph development in the one-leaf species Monophyllaea glabra. METHODS: Mitotic activities of meristem cells were monitored by incorporation of a thymidine analog (EdU) into DNA. Orthologs of SHOOTMERISTEMLESS (STM) and PHANTASTICA, ROUGH SHEATH2, ASYMMETRIC LEAVES1 (PHAN/RS2/AS1) were isolated from M. glabra, and their expression patterns were investigated by quantitative reverse transcription polymerase chain reaction in combination with a laser microdissection technique. KEY RESULTS: Mitotic activities were detected in all three phyllomorph meristems. Strong expression of the STM and PHAN/RS2/AS1 orthologs was detected in the vegetative GM and BM, respectively. CONCLUSIONS: The vegetative GM is an active meristem that expresses the STM ortholog. We postulate that the GM is required for growth of a phyllomorph by providing undifferentiated cells and/or growth regulators to the BM and/or PM.
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