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J Integr Plant Biol. 2015 Sep;57(9):757-69. doi: 10.1111/jipb.12363. Epub 2015 Jun 23.

Characterization of tub4(P287L) , a β-tubulin mutant, revealed new aspects of microtubule regulation in shade.

Yu J1,2, Qiu H1,2, Liu X1, Wang M1, Gao Y1, Chory J3,4, Tao Y1,2.

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School of Life Sciences, Xiamen Plant Genetics Key Laboratory, Xiamen University, Xiamen, 361102, China.
State Key Laboratory of Cellular Stress Biology, Xiamen University, Xiamen, 361102, China.
Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, California, 92037, USA.
Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California, 92037, USA.


When sun plants, such as Arabidopsis thaliana, are under canopy shade, elongation of stems/petioles will be induced as one of the most prominent responses. Plant hormones mediate the elongation growth. However, how environmental and hormonal signals are translated into cell expansion activity that leads to the elongation growth remains elusive. Through forward genetic study, we identified shade avoidance2 (sav2) mutant, which contains a P287L mutation in β-TUBULIN 4. Cortical microtubules (cMTs) play a key role in anisotropic cell growth. Hypocotyls of sav2 are wild type-like in white light, but are short and highly swollen in shade and dark. We showed that shade not only induces cMT rearrangement, but also affects cMT stability and dynamics of plus ends. Even though auxin and brassinosteroids are required for shade-induced hypocotyl elongation, they had little effect on shade-induced rearrangement of cMTs. Blocking auxin transport suppressed dark phenotypes of sav2, while overexpressing EB1b-GFP, a microtubule plus-end binding protein, rescued sav2 in both shade and dark, suggesting that tub4(P287L) represents a unique type of tubulin mutation that does not affect cMT function in supporting cell elongation, but may affect the ability of cMTs to respond properly to growth promoting stimuli.


Arabidopsis; microtubules; plant hormones; shade

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