3.  Changes in Gene Expression during Gravistimulation

A terminally differentiated higher plant cell expresses an array of genes required for fulfilling its normal, stable metabolic role. However, when changes in environmental conditions occur, the cell can respond in a rapid and specific manner by selectively increasing or decreasing the expression of specific genes.  Genes whose expression is increased during times of gravistimulation presumably are critical to the adaptation of the organism to a changing environment.

Objectives: The objective of this project is to investigate the changes in gene expression after gravistimulation (change in orientation to gravity) in plant stems. Gravistimulation alters the pattern of cellular growth along the stem resulting in a characteristic upward gravitropic curvature. These changes in cell growth are necessarily linked to enzymatic activities in the cell wall which facilitate loosening of the matrix and increase elasticity in growing cells. The major studies will include:

(1)   Analysis of the soluble cell wall and cytoplasmic proteins during gravitropic curvature.

(2)   Amino acid sequence analysis of novel proteins associated with gravistimulation.

Project Importance: Since NASA is currently designing plant growth facilities in space, changes in gene expression and response to gravity is of critical importance.  These concepts represent basic information in the evaluation of plant requirements for growth in a closed environment under microgravity or zero gravity conditions. The goals of this project are consistent with those currently supported by NASA's Space Biology Program in that they address the transduction of plant's response to gravity.