February 6, 2018
New pathways that contribute to root elongation
A RIKEN CSRS–University of Tokyo collaborative team has discovered that two transcription factors involved in the unfolded protein response (UPR), a stress responsive transcription pathway triggered by the endoplasmic reticulum (ER), are essential to the normal elongation of plant roots.
The general growth of a plant is affected by various stresses such as high temperatures, drought and disease. In Arabidopsis thaliana, three bZIP transcription factors have been reported to modulate UPR. Of these three, bZIP28 and bZIP60 are known major factors contributing to the tolerance of various environmental stresses. However, the function of bZIP17 has not been well understood.
The collaborative team successfully generated a double knockout mutant for bZIP17and bZIP28, which has been assumed to be lethal. The single knockout (KO) mutant plants of bZIP17 and bZIP28 demonstrated the same development and growth as their wild-type counterparts, but the double KO mutant roots grew only to about 10 percent of the wild-type controls. Researchers also found that the expression of multiple cell elongation genes was significantly suppressed in the double KO mutant. These concurrence suggested that UPR functions not only in terms of stress responses, but also plays a special role in controlling root elongation through bZIP17 and bZIP28.
Further analysis of the molecular mechanisms that UPR uses to control root elongation should deepen understanding of this ER stress signaling–inclusive mechanism. Moreover, clarifying the causative genes linking bZIP and root elongation is expected to lead to technological developments for crop improvement.
Plant Physiology doi:10.1104/pp.17.01414
J.-S. Kim, K. Yamaguchi-Shinozaki, K. Shinozaki,
"ER-Anchored Transcription Factors bZIP17 and bZIP28 Regulate Root Elongation".
June-Sik Kim; Special Postdoctoral Researcher
Kazuo Shinozaki; Group Director
Gene Discovery Research Group