REGULATION OF THE MAIZE MIR172 MICRORNA AND ITS TARGETS BY GIBBERELLIC ACID
Plant Gene Expression Center Albany_CA
2012 Annual Report
1a.Objectives (from AD-416):
Our objective is to uncover the molecular pathways necessary for causing developmental transitions in maize and manipulate them to improve crop plants.
1b.Approach (from AD-416):
1. Examine the response of the miR172 gene family and its targets to gibberellic acid (GA).
2. Determine the function of target genes of the miR172 gene family member, tasselseed4 (ts4), and their interactions with GA.
3. Identify downstream targets of select target genes.
4. Determine the effects of altering miR172 expression.
5, Create gain-of-function phenotypes for select target genes by altering the miR172 binding site.
The project relates to all three objectives of the parent project. The expression of miR172 in GA mutant backgrounds, and in mutants rescued with exogenous GA was assayed by microRNA northern blots. miR172 expression was found to be reduced in GA deficient mutants, but restored to normal levels upon rescue with GA spray. This same pattern was also seen with the brassinosteroid mutant nana1, indicating that several hormone networks may converge to regulate miR172 expression.
Loss of function transposon knockout mutants have now been isolated in five of the six known AP2 target genes of miR172. In addition to the two already published on, knockouts in a pair of duplicated target genes named zmlipless1 and sister of zmlipless1 have been identified that together appear to play roles in the specification of floral organ identity.