Figure 8
A working model describing the link between CSN6, CUL1, IDEF1 and iron nutrition in rice.
On the early stage of -Fe or in CSN6 antisense lines, CSN6 expression is down-regulated. Reduced CSN6 leads to reduced expression of CSN5 and COP9 activity (derubylation of CRL), thus retarding the proteasomal degradation of IDEF1, leading to the accumulation of HMW-IDEF1 protein. Elevated IDEF1 up-regulates iron utilisation-related genes such as IRO2, IRT1, YSL15, and NASs, contributing to chlorophyll and iron concentration accumulation. On the later days of -Fe or in sense CSN6 lines, the derubylation activity of CSN is reactivated as a result of increased CSN6 transcription. The excess IDEF1 protein is degraded via proteasome-mediated degradation. Treatment with MG132 leads to the accumulation of IDEF1, reminiscent of antisense lines and the HMW-IDEF1 is linked to K48-polyubiquitin chains. MLN4924 can suppress the rubylation of CUL1 in rice. HRZs are guessed to be the F-box (E3) involved in IDEF1 degradation.
