Recently, researchers from Biotechnology Research Institute in CAAS have published a research paper entitled “The Ubiquitin-Binding Protein OsDSK2a Mediates Seedling Growth and Salt Responses by Regulating Gibberellin Metabolism in Rice”on December 11 in Plant Cell. This study revealed the molecular mechanism of the modulation of ubiquitin-binding protein OsDSK2a in coordinating plant growth and salt-stress responses through regulating the level of the gibberellin (GA) metabolism regulator ELONGATED UPPERMOST INTERNODE (EUI) in rice.

UBL-UBA (ubiquitin-like-ubiquitin-associated) proteins are ubiquitin receptors and transporters in the ubiquitin-proteasome system that play key roles in plant growth and development. High salinity restricts plant growth by disrupting cellular metabolism, but whether UBL-UBA proteins are involved in this process is unclear.

This study reported that loss-of-function mutant of OsDSK2a, encoding an UBL-UBA protein, shows retarded seedling growth and contains reduced bioactive GAs. They demonstrated that OsDSK2a combines with polyubiquitin chains and interacts with the GA-deactivating enzyme EUI, resulting in its degradation through the ubiquitin-proteasome system. By contrast, eui mutants displayed increased seedling growth and bioactive GA levels. OsDSK2a levels decreased in plants under salt stress. Moreover, EUI accumulated under salt stress more rapidly in osdsk2a than in wild-type plants. Thus, OsDSK2a and EUI play opposite roles in regulating plant growth under salt stress by affecting GA metabolism. Under salt stress, OsDSK2a levels decrease, thereby increasing EUI accumulation, which promotes GA metabolism and reduces plant growth. This study unveils a previously unrecognized mechanism whereby salt stress restricts seedling growth by interfering with the OsDSK2a-EUI complex through modulating GA homeostasis.
 

Salinity is a major factor limiting crop productivity. Rice, a staple crop for the majority of the world, is highly sensitive to salinity stress. Improving salt tolerance of rice is an effective means of making use of saline-alkali land and increasing crop yield. This study will help breeders to use this knowledge to guide breeding of salt-tolerant crop plants.

This research was funded by the National Key Research and Development Program of China (2016YFD0100604), the National Natural Science Foundation of China (31470366 and 31771706) and Agricultural Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences.

More details are available at: http://www.plantcell.org/content/early/2019/12/11/tpc.19.00593.long