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Molecular Breeding

, Volume 34, Issue 1, pp 47–57 | Cite as

Regulation of the α-expansin gene OsEXPA8 expression affects root system architecture in transgenic rice plants

  • Ying Wang
  • Nana Ma
  • Shichun Qiu
  • Hanyan Zou
  • Guangchao Zang
  • Zhenhui Kang
  • Guixue Wang
  • Junli HuangEmail author
Article

Abstract

Expansins are cell wall proteins implicated in the control of plant growth via loosening of the extracellular matrix, and are encoded by a large gene family. However, data linked to loss of function of single genes which support the role of expansins in root growth remain limited. In this study, we used RNA interference to examine the biological functions of the rice α-expansin gene OsEXPA8. Repression of OsEXPA8 expression in rice impaired the root system architecture and plant growth significantly, leading to shorter primary roots and fewer lateral roots. Accordingly, the cell size of the root vascular bundle reduced drastically. Notably, OsEXPA8 silencing impaired root hair elongation; moreover, plant height was clearly reduced. Transient expression of OsEXPA8-GFP in onion epidermal cells verified that OsEXPA8 is located on the cell wall. OsEXPA8 was expressed predominantly in the root and shoot of one-week-old rice seedlings, and highly induced by NaCl but suppressed by nitrate and phosphate starvation. In addition, atomic force microscopy was used to explore alterations in cell wall nanomechanics caused by OsEXPA8 protein reduction, which showed that the wall stiffness (Young’s modulus) of OsEXPA8-silenced suspension cells was increased significantly. Taken together, our results suggest that OsEXPA8 is critical for root system architecture, which supports the hypothesis that expansins are involved in enhancing plant growth by mediating cell wall loosening.

Keywords

α-Expansin Rice Root system architecture OsEXPA8 Atomic force microscopy (AFM) Elastic (Young’s) modulus Cell expansion 

Notes

Acknowledgments

This work was supported by the National Natural Science Foundation of China (31271685, 30900882), National Genetically Modified Organisms Breeding Major Projects (2009ZX08009-109B), Chongqing Municipal Science and Technology Commission projects (CSCT 2012GGC80002) and the National “111 plan” (B06023) as well as the Public Experiment Center of State Bioindustrial Base (Chongqing).

Conflict of interest

As the corresponding author, I declare on behalf of all co-authors that there are no conflicts of interest regarding this manuscript.

Supplementary material

11032_2014_16_MOESM1_ESM.doc (32 kb)
Supplementary material 1 (DOC 32 kb)
11032_2014_16_MOESM2_ESM.tif (574 kb)
Fig. S1 Stiffness-properties by AFM techniques. (a) Optical image of a typical single rice cell sample. The shadow of the AFM cantilever is visible on the left-hand side of the image. (b) A typical force-distance (FD) curve recorded on a single rice cell sample. The upper line represents the FD curve when the tip indents (or penetrates) the cell wall and the lower line represent the FD curve when the tip retracts from the cell wall. (TIFF 574 kb)
11032_2014_16_MOESM3_ESM.tif (88 kb)
Fig. S2 Effects of OsEXPA8 down-regulation on the root system architecture. (a) Primary root length of one-week-old seedlings. (b) Lateral root density of one-week-old rice seedlings. Two independent transgenic lines (line 3 and line 6) were analyzed. The seeds were placed on solid half-strength MS solid medium and grown for 7 days vertically in a growth chamber. Values are the means of ten biological replications ± standard error. One independent plant was considered as one biological replication. The asterisk indicates significantly different from the control (t-test, P < 0.01). (TIFF 87 kb)
11032_2014_16_MOESM4_ESM.tif (105 kb)
Fig. S3 The wall stiffness profiles of wild-type (a), (c), (e) and OsEXPA8-silenced suspension cells (b), (d), (f) with the passage of time in culture. (a) and (b) on day 5, (c) and (d) on day 10, (e) and (f) on day 13. (TIFF 105 kb)
11032_2014_16_MOESM5_ESM.tif (80 kb)
Fig. S4 Expression levels of OsEXPA3 and OsEXPA9 in the root of OsEXPA8-silenced roots (line 3). The asterisk indicates significantly different from the wild type (t-test, P < 0.01). (TIFF 80 kb)

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Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  • Ying Wang
    • 1
  • Nana Ma
    • 1
  • Shichun Qiu
    • 1
  • Hanyan Zou
    • 1
  • Guangchao Zang
    • 1
  • Zhenhui Kang
    • 1
  • Guixue Wang
    • 1
  • Junli Huang
    • 1
    Email author
  1. 1.Key Laboratory of Biorheological Science and Technology, Ministry of Education, Bioengineering CollegeChongqing UniversityChongqingPeople’s Republic of China

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