UC Riverside

ABSTACT OF THE THESIS

Function of TPPI and TPPJ in Arabidopsis Boundary Regions

by

Jessica Lynn Lor

Master of Science, Graduate Program in Plant Biology

University of California, Riverside, December 2014

Dr. Patricia Springer, Chairperson

The shoot apical meristem (SAM) located at the shoot tip of a plant, produces all above ground organs including leaves and flowers. Separating the SAM and a lateral organ is the boundary region, which has distinctive cellular properties. The boundary region has many important functions including organ separation and axillary meristem formation. It is known that LATERAL ORGAN BOUNDARIES (LOB), an organ boundary gene, plays a role in organ separation by limiting growth in the boundary region. Through microarray and qRT-PCR, a TREHALOSE PHOSPHATE PHOSPHATASE gene, TPPJ, has been identified as a potential downstream target of LOB. Trehalose phosphate phosphatases (TPPs) are known to regulate the production of metabolic intermediates of the trehalose biosynthesis pathway in plants. The overall objective of this research was to investigate the function of TPPJ and its paralog, TPPI, in the boundary region of Arabidopsis. The first goal was to characterize TPPI and TPPJ loss-of-function mutants in order to determine if these genes have a function in the boundary region. The second goal was to characterize the genetic relationship between LOB and TPPI and TPPJ using genetic and transgenic approaches. It was discovered that the tppj-sk T-DNA insertion line has reduced levels of TPPJ transcript. Furthermore, expression of TPPJ in the boundary under control of the LOB promoter (pLOB:TPPJ) suppressed organ fusion in the lob-3 mutant, showing TPPJ is sufficient to rescue the lob mutant phenotype. tppi-1 loss-of-function mutants displayed a decurrent strand fusion phenotype, indicating that TPPI also has a role in organ separation. In addition, tppi-1 mutants were late flowering, indicating that TPPI may also be involved in the transition from vegetative to reproductive development. Together, this work provides a starting point for determining the function of TPPI and TPPJ in the boundary region of Arabidopsis.