Regulation of the α-expansin gene OsEXPA8 expression affects root system architecture in transgenic rice plants
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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.
Keywordsα-Expansin Rice Root system architecture OsEXPA8 Atomic force microscopy (AFM) Elastic (Young’s) modulus Cell expansion
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.
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