GSE112080
RNAseq for peach weeping and standard lateral shoot (branch) tips
Plant shoots typically grow upward in opposition to the pull of  gravity. However, exceptions exist throughout the plant kingdom.  Most conspicuous are trees with weeping or pendulous branches.  While such trees have long been cultivated and appreciated for  their ornamental value, the molecular basis behind the weeping  habit is not known. Here, we characterized a weeping tree  phenotype in Prunus persica (peach) and identified the underlying  genetic mutation using a genomic sequencing approach. Weeping  peach tree shoots exhibited a downward elliptical growth pattern  and did not exhibit an upward bending in response to 90° reorientation.  The causative allele was found to be an uncharacterized  gene, Ppa013325, having a 1.8-Kb deletion spanning the 5' end.  This gene, dubbed WEEP, was predominantly expressed in phloem  tissues and encodes a highly conserved 129-amino acid protein  containing a sterile alpha motif (SAM) domain. Silencing WEEP in  the related tree species Prunus domestica (plum) resulted in more  outward, downward, and wandering shoot orientations compared  to standard trees, supporting a role for WEEP in directing lateral  shoot growth in trees. This previously unknown regulator of  branch orientation, which may also be a regulator of gravity per-  ception or response, provides insights into our understanding of  how tree branches grow in opposition to gravity and could serve  as a critical target for manipulating tree architecture for improved  tree shape in agricultural and horticulture applications. Overall design: mRNA was isolated from four shoot tips (approximately 4cm long) from standard and weeping peach trees. Four biological replicates for each type of tree were sequenced using illumina Hiseq2000