Regulation of Expansin Gene Expression Affects Growth and Development in Transgenic Rice Plants

Abstract

To investigate the in vivo functions of expansins, we generated transgenic rice plants that express sense and antisense constructs of the expansin gene OsEXP4 . In adult plants with constitutive OsEXP4 expression, 12% of overexpressors were taller and 88% were shorter than the average control plants, and most overexpressors developed at least two additional leaves. Antisense plants were shorter and flowered earlier than the average control plants. In transgenic plants with inducible OsEXP4 expression, we observed a close correlation between OsEXP4 protein levels and seedling growth. Coleoptile and mesocotyl length increased by up to 31 and 97%, respectively, in overexpressors, whereas in antisense seedlings, they decreased by up to 28 and 43%, respectively. The change in seedling growth resulted from corresponding changes in cell size, which in turn appeared to be a function of altered cell wall extensibility. Our results support the hypothesis that expansins are involved in enhancing growth by mediating cell wall loosening.

SAMBA, a plant-specific anaphase-promoting complex/cyclosome regulator is involved in early development and A-type cyclin stabilization

“…This hypothesis is supported by the expression analysis of cell cycle marker genes that revealed a more rapid down-regulation of mitotic genes and an up-regulation of the cell cycle inhibitory genes in the samba mutants. The EXP11 gene expression was also upregulated, in agreement with data showing that the ectopic expression of EXPANSIN genes stimulate plant growth and suppression by gene silencing reduces it (42,43). Furthermore, microarray analysis showed that in samba knockout plants, the ethylene signal transduction was clearly overrepresented, which plays a prominent role in cell division regulation during leaf development by arresting the cell cycle (44).…”

Combined Large-Scale Phenotyping and Transcriptomics in Maize Reveals a Robust Growth Regulatory Network

“…Expression levels of b-EXPANSIN4, another cell wallloosening enzyme, were negatively correlated with leaf size traits (Fig. 7), although up-and down-regulation of expansin expression in Arabidopsis and rice resulted in larger and smaller leaves, respectively (Cho and Cosgrove, 2000;Choi et al, 2003;Goh et al, 2012). However, more pleiotropic phenotypes were observed after constitutive modification of expansin gene expression, including a reduction in overall plant growth (Rochange and McQueen-Mason, 2000), demonstrating that the effect of expansin expression on leaf growth is context dependent and influenced by the growth phase of the leaf (Sloan et al, 2009).…”

Ethylene-Mediated Acclimations to Flooding Stress

“…Exogenous ABA application restricts elongation because of reduced tissue responsiveness to GA. Farther downstream, induction of the expression and activity of expansins facilitates cellular expansion and growth (Choi et al, 2003). Shoot elongation is a quantitative trait attributed primarily to the SNORKEL (SK) locus on chromosome 12, which together with two other loci on chromosomes 1 and 3, can account for the full escape response (Hattori et al, 2008(Hattori et al, , 2009(Hattori et al, , 2011.…”