Recently, researchers from LI Yunhai’s group in the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), collaborating with Dirk Inzé’ group in Ghent University, revealed that STERILE APETALA modulates the stability of a repressor protein complex to control organ size in Arabidopsis thaliana.
Organ size is coordinately controlled by cell proliferation and cell expansion. During Arabidopsis leaf development, the leaf primordia firstly undergo extensive cell division to increase cell number, following a transition from cell proliferation to cell expansion. When most cells begin to differentiate and enlarge, some cells so called meristemoids divide a few rounds and give rise to stomata or epidermal pavement cells. In Arabidopsis, the proliferation of meristemoid cells contributes significantly to leaf size. However, little is known about how the division of meristemoid cells controls final organ size.
Previous studies by LI Yunhai’s group and Dirk Inzé’ group have shown that F-box protein STERILE APETALA (SAP)/SUPPRESSOR OF DA1 (SOD3) influents the stability of the transcriptional regulators PEAPODs (PPDs) and then promotes meristemoid proliferation and regulates organ size. In their recent report, they identified KIX8 and KIX9 as novel substrates of SAP through yeast two-hybrid screening.
They demonstrated that SAP interacts with KIX8 and KIX9 in vitro and in vivo, and affects their protein stability. KIX8 and KIX9 have previously been shown to function as adaptors for the corepressor TOPLESS and PPD. They further performed genetic analysis and showed that the kix8 kix9 mutant can suppress the organ size phenotypes of sod3, and the ppd2 mutant can further suppress the organ size phenotypes of sod3 kix8 kix9. These results suggested that SAP acts in a common genetic pathway with KIX and PPD to control organ growth. This conclusion was reinforced by analyses of the proliferation of meristemoid cells and the expression of PPD2 target genes.
This study revealed that SAP targets the KIX-PPD repressor complex for degradation to regulate meristemoid cell proliferation and organ size.
This work entitled “STERILE APETALA modulates the stability of a repressor protein complex to control organ size in Arabidopsis thaliana” was online published in PLOS Genetics on Feb 5, 2018.
This research was supported by grants from the National Natural Science Foundation of China and the Strategic Priority Research Program of CAS.
A genetic and molecular framework for SAP, KIX and PPD-mediated regulation of meristemoid cell proliferation and organ size (Image by IGDB)
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