Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Oral Communication Abstract - S4b

KNOX GENES IN PLANT HORMONE METABOLISM AND SIGNAL TRANSDUCTION

G. FRUGIS*, D. MARIOTTI*, N.-H. CHUA**

*) Istituto di Biologia e Biotecnologia Agraria (IBBA), CNR, Area della Ricerca di Roma, Via Salaria Km. 29,300, 00016 Monterotondo Scalo (Roma), IT

**) Laboratory of Plant Molecular Biology, Rockefeller University, 1260 York Avenue, 10021 New York, NY – USA

hormones, transcription factors, Arabidopsis thaliana, KNOX

KNOX transcription factors have an important role in the shoot apical meristem formation a maintenance. Overexpression of knox genes, similar to the KN1 gene from maize, in different species causes strong alteration of cell fate with dramatic changes of the whole plant architecture and leaf morphology. Several studies have suggested that knox genes might affect cytokinins and gibberellins homeostasis as transgenic plants or mutants that misexpress knox factors display altered levels of these hormones.

STM is the only KNOX gene which mutation completely prevents embryonic shoot apical meristem formation. Weak stm alleles display alteration of meristem activity and abnormal flower morphology. On this base, it was hypothesized that STM is required for both SAM formation and function during the whole life of the plant. STM target genes have not been isolated so far and little information is available on the possible hormone pathways through which it may act to control meristem formation and activity during different phases of plant development. Evidences for genetic interactions among STM, CUC genes (member of the NAC transcription factor family) and PIN1 and MP (genes involved in auxin transport and localization) have been recently found.

To better characterize STM function in plant development and a possible connection to auxin transport, we produced and characterize Arabidopsis transgenic plants in which STM expression is either increased (constitutively or in a glucocorticoid-induced fashion) or silenced through RNA interference technology. We also analyzed auxin distribution and both auxin and gibberellin responses in plants that misexpress STM in order to identify the hormone biosynthesis or signaling pathways through which STM exerts its key role in meristem function.