Specific roles of AtEXPA1 in plant growth and stress adaptation

Expansins are a group of proteins that appear to be involved in the disruption of the noncovalent bonds within the cell wall. The distinctly expressed expansin genes can independently regulate cell expansion in place and time, and their diverse expression patterns suggest their distinct effects on plant growth. In this paper, we analyzed the effects of excessive expansin AtEXPA1 on plant growth and plant adaptation to NaCl and ABA stresses by overexpressing its gene in Arabidopsis plants. The AtEXPA1 overexpressing plants exhibited stunted shoot growth, mainly during the early phase of vegetative growth, and the growth of transgenic seedlings was also impaired. Comparing with their growth under normal growth condition, the AtEXPA1 overexpressing plants showed alleviated impairment under salt and ABA stress conditions. These results suggest that, although excessive AtEXPA1 could disturb cell wall organization and lead to growth reduction, it inversely helped enhancing cell wall organization under stress conditions and thus helped plant better to adapt to adverse environment.