Abstract
To understand how plant growth is sustained under environmental stress conditions, we have analyzed salt sensitive mutants of rice. RSS3 (Rice Salt Sensitive3) was identified originally as a gene required for normal root growth under mild salinity condition. Recent analysis showed that rss3 mutant exhibits both salt-dependent and independent phenotypes; Under non-stress conditions, rss3 shows moderate decrease of the number of crown roots and reduction of cell elongation. When grown under salt stress, the root growth of rss3 is more severely impaired, along with morphological aberrancy, resulting in a wavy root phenotype. In this study, we report that aberrant cellular arrangement is frequently observed in the meristematic region of the rss3 root. RSS3 encodes a nuclear-localized protein, which has a putative regulatory domain, highly conserved among a class of plant bHLH transcription factors, but lacks a DNA binding domain. RSS3 is highly expressed in roots, especially in the meristematic zone. These results raise a possibility that RSS3 may regulate gene expression in the root meristem, by modulating the activity of transcription factor(s).
