期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：15
页码：4821-4826
DOI：10.1073/pnas.1503998112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThe phytohormone indole-3-acetic acid (IAA) plays a vital role in plant growth and development. IAA can be synthesized through the precursor tryptophan (Trp), known as the Trp-dependent IAA biosynthetic pathway. However, IAA may also be synthesized through a proposed Trp-independent IAA biosynthetic pathway. Although the Trp-independent IAA biosynthesis was hypothesized 20 years ago, it remains a mystery. In this paper, we provide compelling evidence that the cytosol-localized indole synthase (INS) initiates the Trp-independent IAA biosynthetic pathway and that the spatial and temporal expression of INS plays an important role in the establishment of the apical-basal pattern during early embryogenesis, demonstrating that the Trp-dependent and -independent IAA biosynthetic pathways coordinately regulate embryogenesis of higher plants. The phytohormone auxin regulates nearly all aspects of plant growth and development. Tremendous achievements have been made in elucidating the tryptophan (Trp)-dependent auxin biosynthetic pathway; however, the genetic evidence, key components, and functions of the Trp-independent pathway remain elusive. Here we report that the Arabidopsis indole synthase mutant is defective in the long-anticipated Trp-independent auxin biosynthetic pathway and that auxin synthesized through this spatially and temporally regulated pathway contributes significantly to the establishment of the apical-basal axis, which profoundly affects the early embryogenesis in Arabidopsis. These discoveries pave an avenue for elucidating the Trp-independent auxin biosynthetic pathway and its functions in regulating plant growth and development.
