Location: Plant Gene Expression Center2011 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.
3. Progress Report
The effects of hormones on miR172 expression were examined using microRNA northern blots. miR172 levels were greatly decreased in the shoot apices of several GA biosynthetic maize mutants as well as mutants defective in GA response. These results indicate that GA biosynthesis and perception act upstream of miR172 to activate its expression. The promoters of several miR172 genes in grasses and dicots are currently under analysis to identify common GA response elements active during the juvenile phase of development. Chromatin immunoprecipitation was used to identify targets of the AP2 gene branched silkless1 (bd1) based on the presence of bd1 binding sequences in their promoters. Preliminary evidence suggests that another AP2 gene, indeterminate spikelet1, may be a target of bd1. In addition, a second transcription factor responsible for floral initiation called zmLFY also appears to be a target. High through put sequencing of ChiP DNA is currently being used to identify additional targets of bd1.