Introduction

Plants use photosynthesis to harness light energy and convert it to chemical energy in the form of sugars and starches. The protein ribulose bisphosphate carboxylase (RUBISCO) plays an important role in fixing and binding carbon in the photosynthetic pathway. The RUBISCO protein is composed of a larger subunit, RBCL, and smaller subunit. The larger subunit is transcribed from the chloroplast genome and thus can be studies by looking at chloroplast quantification and gene expression. Chloroplast content (Klein and Mullet, 1987) and the production of several proteins, not including RBCL, (Baena-Gonzalez et al.,2001) in leaf structures increases at higher light intensities . In contrast to chloroplast quantity, studies have shown that chloroplast nucleic acid content (Klein and Mullet, 1987) as well as transcription levels (Gall, et al., 1996) have decreased in plants treated with higher light intensities. Using this background information, we hope to elucidate the expression of RBCL as it relates to light intensity in flowering plants. In addition, although no information was found that specifically highlighted the change in RBCL production when flowering plants are grown in non-optimal light conditions; we predict that non-optimal growth conditions will effect the variation of chloroplast content to RBCL transcription.

Plant Selection and Setup

Vinca ‘Nirvana Cascade’ was selected for the species that grow best in full sunlight. For our shade loving species, Impatiens sp. were chosen. Plants were obtained from Lowes Hardware where they were held in similar climatic conditions. One of each plant was grown in full sun and the other in full shade outside in early fall of a temperate climate. After a growing period of 4 days, leaves were harvested from all plants and stored at -80º C.

We hypothesize that plant species which require higher light intensities will have more chloroplasts with lower RBCL expression per chloroplast and species that grow best in full shade will have lower chloroplast content with higher RBCL levels per chloroplast. In addition, by placing species in non-optimal light conditions, the plant will attempt to adjust chloroplast and RBCL levels to most effectively use available light. By manipulating the sunlight these plants receive and then using Western Blot to semi-quantitate RBCL levels; the expression level can be related to the number of relative copies of RBCL gene (determined by Real Time PCR).

Vinca 'Nirvanna Cascade" http://www.prairiestarflowers.com

Impatiens
http://escambia.ifas.ufl.edu/impatiens.JPG