P0829 Quantitative Differential Gene Expression in Peach during Short-day Induced Growth Cessation

Christina Wells , School of Agricultural, Forest & Environmental Sciences, Clemson University, Clemson, SC
Alex Feltus , Genetics & Biochemistry, Clemson University, Clemson, SC
Gregory L. Reighard , School of Agricultural, Forest & Environmental Sciences, Clemson University, Clemson, SC
Douglas G. Bielenberg , School of Agricultural, Forest & Environmental Sciences, Clemson University, Clemson, SC
Perception of short days (SD) triggers growth cessation, bud formation, dormancy entrance, and  establishment of chilling requirement in many tree species. However, the peach evergrowing (evg) mutant fails to cease elongation growth in response to SD exposure.  We previously associated this mutation with the loss of expression of six dormancy-associated MADS-box (DAM) genes.  Here we investigate molecular pathways downstream of the DAM genes to further our mechanistic understanding of the yearly cycle of growth and dormancy in perennial species. We grew F2 sibling wild-type (wt) and evg trees in long day (LD, 16 hour photoperiod) conditions,  then reduced the photoperiod to 8 hours (SD). Apical regions, including the terminal bud and youngest leaves, were sampled at 0, 1, and 2 weeks following the SD transition.  Over the 2-wk interval, elongation growth of wt trees was visibly reduced, while that of mutant trees was unaffected. Pooled mRNA samples from 20 trees of each genotype x time combination were extracted, quality checked, and sequenced with Illumina™ GAII technology. We obtained approximately 50 million reads, which were used to assemble and quantify  expression of all peach transcripts in wt and evg samples at each time point. As well as exhibiting no DAM gene expression, evg trees failed to express constans (CO) and showed no SD-induced reduction in the expression of a terminal flower 1 (TFL-1) homolog. While the peach genome contains a distant homolog of flowering locus C (FLC), its transcript was not detected under any conditions.