The SOR1-OsIAA26 signal module specially regulates the ethylene reaction at the root of the rice.

Plant hormones growth hormones and ethylene co-regulate the growth of plant roots.
ethylene promotes the synthesis and transport of growth hormone, the growth receptor TIR1/AFB2 feels growth hormone, combines and uphred transcription inhibitor Aux/IAA protein, so that it degrades through the 26S protease pathway, thus releasing transcription factor ARF to regulate the expression of downstream genes.
the current growth hormone signaling process of mediated ethylene reaction is not clear.
Zhang Jinsong of the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences and Chen Yuyi' research team identified a new factor MHZ2/SOR1 in the ethylene reaction of the specific regulatory root of TIR1/AFB2 downstream by screening the insensitive mutants of rice ethylene, and analyzed the signal transduction mechanism of SOR1 participating in the growth hormone-mediated ethylene reaction.
studies have found that SOR1 is a plant-specific E3 ubiquitin connecting enzyme that interacts with the OsIAA26 protein and regulates its ubiquitic degradation.
, SOR1 can also interact with the OsIA9 protein, but it cannot ubiquitize the OsIAA9 protein, in turn, the OsIAA9 protein can inhibit SOR1's E3 ubiquitin connective activity.
unlike OsIAA9, OsIAA26 is an atypical Aux/IAA protein that cannot be combined with TIR1/AFB2.
in the absence of ethylene or growth hormone, OsIAA9 indirectly stabilizes the OsIAA26 protein by binding SOR1 to inhibit its E3 connective activity, and in the case of ethylene or growth hormone, TIR1/AFB2 binding OsIAA9 degrades it, thus releasing SOR1 to regulate the degradation of the OsIA26 protein.
this novel result reveals that the SOR1-OsIAA26 signal module is located downstream of the TIR1/AFB2-auxin-OsIA9 signal, and specially regulated ethylene reaction at the root of the rice.
the results were published online April 10 in the Proceedings of the National Academy of Sciences (PNAS) (DOI: 10.1073/pnas.1719387115). Chen Hui, a graduate of the
Research Group, An associate researcher Ma Wei and Ph.D. student Zhou Yang are the co-first authors of the paper.
Xie Qi Research Group was also involved in the study.
the research was funded by the National Natural Science Foundation of China, the "973" project of the Ministry of Science and Technology of China and the National Key Laboratory for Plant Genomics.
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