Fig 8. Hypothetical model for the regulation of ovule development by RNA processing.

Proposed model for the influence of the HUA-PEP activity on ovule development upon environmental constraints. A) The HUA-PEP activity proteins facilitate pre-mRNA processing and hence production of functional AG and D-class proteins (purple circles). Under favorable conditions, AG, SHPs and STK are produced at a high rate, enough to properly regulate development of ovules (AG, SHPs, STK) and seeds (SHPs, STK). B) Upon mutation of the HUA-PEP activity genes, and possibly under stress conditions, premature transcript termination of AG and D-class gene pre-mRNAs might result in a critical decrease of transcripts encoding the corresponding functional proteins. Then, adequate development should be disrupted and instead ovule abortion occurs. Further reduction of ovule identity gene activities should account for homeotic transformations of ovules into flower organ-like structures.