Wyatt Sarah E, Rashotte Aaron M, Shipp Matthew J, Robertson Dominique, Muday Gloria K
Department of Botany, North Carolina State University, Raleigh 27695-7612, USA.
Plant Physiol. 2002 Nov;130(3):1426-35. doi: 10.1104/pp.102.010579.
Gravity plays a fundamental role in plant growth and development, yet little is understood about the early events of gravitropism. To identify genes affected in the signal perception and/or transduction phase of the gravity response, a mutant screen was devised using cold treatment to delay the gravity response of inflorescence stems of Arabidopsis. Inflorescence stems of Arabidopsis show no response to gravistimulation at 4 degrees C for up to 3 h. However, when gravistimulated at 4 degrees C and then returned to vertical at room temperature (RT), stems bend in response to the previous, horizontal gravistimulation (H. Fukaki, H. Fujisawa, M. Tasaka [1996] Plant Physiology 110: 933-943). This indicates that gravity perception, but not the gravitropic response, occurs at 4 degrees C. Recessive mutations were identified at three loci using this cold effect on gravitropism to screen for gravity persistence signal (gps) mutants. All three mutants had an altered response after gravistimulation at 4 degrees C, yet had phenotypically normal responses to stimulations at RT. gps1-1 did not bend in response to the 4 degrees C gravity stimulus upon return to RT. gps2-1 responded to the 4 degrees C stimulus but bent in the opposite direction. gps3-1 over-responded after return to RT, continuing to bend to an angle greater than wild-type plants. At 4 degrees C, starch-containing statoliths sedimented normally in both wild-type and the gps mutants, but auxin transport was abolished at 4 degrees C. These results are consistent with GPS loci affecting an aspect of the gravity signal perception/transduction pathway that occurs after statolith sedimentation, but before auxin transport.
重力在植物生长发育中起着基础性作用，然而对于向重力性的早期事件却知之甚少。为了鉴定在重力反应的信号感知和/或转导阶段受影响的基因，设计了一个突变体筛选实验，利用冷处理来延迟拟南芥花序茎的重力反应。拟南芥的花序茎在4℃下长达3小时对重力刺激无反应。然而，当在4℃下进行重力刺激，然后在室温（RT）下恢复垂直时，茎会因之前的水平重力刺激而弯曲（H. Fukaki、H. Fujisawa、M. Tasaka [1996]《植物生理学》110: 933 - 943）。这表明重力感知发生在4℃，但向重力性反应并非如此。利用这种对向重力性的冷效应筛选重力持续信号（gps）突变体，在三个位点鉴定出了隐性突变。所有这三个突变体在4℃重力刺激后反应改变，但在室温下对刺激的表型反应正常。gps1 - 1在恢复到室温后对4℃重力刺激不弯曲。gps2 - 1对4℃刺激有反应，但弯曲方向相反。gps3 - 1在恢复到室温后反应过度，继续弯曲到比野生型植物更大的角度。在4℃时，含淀粉的平衡石在野生型和gps突变体中都正常沉降，但在4℃时生长素运输被阻断。这些结果与GPS位点影响重力信号感知/转导途径中发生在平衡石沉降之后、生长素运输之前的某个方面一致。
