Role of the expansin genes NtEXPA1 and NtEXPA4 in the regulation of cell extension during tobacco leaf growth

• Published in: Russian journal of genetics 2014-05, Vol.50 (5), p.489-497
• Main Authors: Kuluev, B. R, Knyazev, A. V, Nikonorov, Y. M, Chemeris, A. V
• Format: Article
• Language: English
• Subjects: Animal Genetics and Genomics; auxins; Biomedical and Life Sciences; Biomedicine; brassinosteroids; cell growth; flowers; gene expression; gene expression regulation; genes; Human Genetics; leaves; messenger RNA; Microbial Genetics and Genomics; Plant Genetics; plant hormones; plant organs; proteins; stems; tobacco
• ISSN: 1022-7954; 1608-3369
• DOI: 10.1134/S1022795414040061

The tobacco plant genes NtEXPA1 and NtEXPA4 encode the α-expansin proteins involved in the regulation of cell growth and extension. We examined the levels of expression of these genes in various plant organs and under the effect of exogenous phytohormones. The highest level of NtEXPA1 expression were registered in the terminal bud and in the young growing leaves and flowers. NtEXPA1 expression ceased once the leaves stopped growing. The NtEXPA4 gene showed a similar expression profile, except for higher levels of mRNA in the leaves. In young leaves located near the terminal bud, high levels of NtEXPA1 and NtEXPA4 are induced by auxins. In the lower leaves, expansin expression is differentially regulated by brassinosteroids, which inhibit NtEXPA1 and upregulate NtEXPA4. We further showed that expression of the transgenic ARGOS-LIKE protein results in upregulation of NtEXPA1 and a reduction in the NtEXPA4 mRNA. In turn, overexpression of NtEXPA1 resulted in an increased size of the leaves and stems because of the larger size of the individual cells.