Abstract
The regulation of hypocotyl elongation is important for plant growth. Microtubules play a crucial role during hypocotyl cell elongation. However, the molecular mechanism underlying this process is not well understood. In this study, we describe a novel Arabidopsis thaliana microtubule-destabilizing protein 25 (MDP25) as a negative regulator of hypocotyl cell elongation. We found that MDP25 directly bound to and destabilized microtubules to enhance microtubule depolymerization in vitro. The seedlings of mdp25 mutant Arabidopsis lines had longer etiolated hypocotyls. In addition, MDP25 overexpression resulted in significant overall shortening of hypocotyl cells, which exhibited destabilized cortical microtubules and abnormal cortical microtubule orientation, suggesting that MDP25 plays a crucial role in the negative regulation of hypocotyl cell elongation. Although MDP25 localized to the plasma membrane under normal conditions, increased calcium levels in cells caused MDP25 to partially dissociate from the plasma membrane and move into the cytosol. Cellular MDP25 bound to and destabilized cortical microtubules, resulting in their reorientation, and subsequently inhibited hypocotyl cell elongation. Our results suggest that MDP25 exerts its function on cortical microtubules by responding to cytoplasmic calcium levels to mediate hypocotyl cell elongation.
Highlights
Etiolation occurs as buried seedlings fully elongate their hypocotyls upward in search of the soil surface
microtubule-destabilizing protein 25 (MDP25) is a protein in Arabidopsis that is homologous with MAP18 (Nagasaki et al, 2008; Kato et al, 2010a), there is no evidence that it directly affects microtubules
We found that the MDP25-green fluorescent protein (GFP) fluorescent signal was still located on the plasma membrane when most cortical microtubules were disrupted, suggesting that the targeting of MDP25 to the plasma membrane was independent of the presence of cortical microtubules
Summary
Etiolation occurs as buried seedlings fully elongate their hypocotyls upward in search of the soil surface. Hypocotyl cells elongate quickly without division during postgermination and are widely used as a model to study the regulation of cell elongation (Gendreau et al, 1997; Wang et al, 2002; TsuchidaMayama et al, 2010). Hypocotyl cells begin their elongation in the basal region. Numerous studies have detailed the mechanisms involved in hypocotyl cell elongation regulated by light, phytohormones, transcription factors, and the cytoskeleton (Wang et al, 2002; Ehrhardt, 2008; Niwa et al, 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
