Date of Award

1-1-2012

Document Type

Campus Access Dissertation

Department

Biological Sciences

First Advisor

Beth A Krizek

Abstract

The shoot apical meristem, a small dome-shaped structure at the shoot apex of higher plants, is established during development of the embryo. After germination, the indeterminate activity of the shoot apical meristem is responsible for the initiation of all aboveground parts of the plant. The shoot apical meristem continuously produces lateral organs on its periphery and provides cells to the elongating stem below the meristem while maintaining a small pluripotent stem cell population. Shoot meristem function is precisely regulated by the combined activities of genetic regulators and plant hormones. We have identified three novel regulators of shoot meristem activity in the model plant Arabidopsis thaliana. These three genes: AINTEGUMENTA (ANT), AINTEGUMENTA-LIKE6 (AIL6) and AINTEGUMENTA-LIKE7 (AIL7) encode related AIL/ PLT transcription factors. Loss of these genes results in plants that produce only a few abnormally-shaped leaves prior to termination of shoot meristem activity. Meristem termination is accompanied by reduced cell division in the meristem region, differentiation of meristematic cells and altered expression of the major meristem regulator genes WUSCHEL (WUS), CLAVATA3 (CLV3) and SHOOT MERISTEMLESS (STM). Genetic studies suggest that ANT, AIL6 and AIL7 do not act specifically in either of two major meristem regulatory pathways: one involving WUS and CLV genes and the other involving STM. Furthermore, these genetic results indicate that ANT, AIL6 and AIL7 have distinct functions within the meristem rather than acting in a strictly redundant manner. We also find that mutations in ANT, AIL6 and AIL7 alter plant hormone responses and/or accumulation although these changes are not strictly correlated with the meristem phenotype. Our study has thus identified three new genes whose distinct functions, perhaps in regulating hormone physiology, are together required for the indeterminate activity of the shoot apical meristem.

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