Tao Zhang,1 Ruonan Li,1 Jialing Xing,1 Lang Yan,1 Rongchen Wang,1 and Yunde Zhao1,2,*
Frontier in Plant Science, 2018; 9: 523.
Published online 2018 Apr 23. doi: 10.3389/fpls.2018.00523
Abstract
A well-developed root system in rice and other crops can ensure plants to efficiently absorb nutrients and water. Auxin is a key regulator for various aspect of root development, but the detailed molecular mechanisms by which auxin controls crown root development in rice are not understood. We show that overexpression of a YUC gene, which encodes the rate-limiting enzyme in auxin biosynthesis, causes massive proliferation of crown roots. On the other hand, we find that disruption of TAA1, which functions upstream of YUC genes, greatly reduces crown root development. We find that YUC overexpression-induced crown root proliferation requires the presence of the transcription factor WOX11. Moreover, the crown rootless phenotype of taa1 mutants was partially rescued by overexpression of WOX11. Furthermore, we show that WOX11 expression is induced in OsYUC1 overexpression lines, but is repressed in the taa1 mutants. Our results indicate that auxin synthesized by the TAA/YUC pathway is necessary and sufficient for crown root development in rice. Auxin activates WOX11 transcription, which subsequently drives crown root initiation and development, establishing the YUC-Auxin-WOX11 module for crown root development in rice.
See: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5925970/
Figure: Overexpression of OsYUC1 promotes crown root proliferation and auxin overproduction. (A) Massive crown root proliferation was observed when OsYUC1 was overexpressed (the right two plants). The overexpression lines initiated many crown roots from the shoots. The crown roots also had more and longer root hairs compared to the wild type plant (left). OsYUC1OX refers to OsYUC1 overexpression under the control of the strong maize UBIQUITIN promoter. OsYUC1OX-1 and OsYUC1OX-3 were two independent TO plants. Bar = 1 cm. (B) Relative transcript levels (folds) of OsYUC1 in the independent overexpression lines. OX refers to OsYUC1 overexpression. WT refers to WT. Note that expression levels in the OX lines were increased hundreds fold. (C) Comparison of IAA contents in whole seedlings of WT and OsYUC1 overexpression tines. The data are presented as mean ±SD (n = 3). ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001 (Student’s t-test).
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