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ARS Home » Northeast Area » Kearneysville, West Virginia » Appalachian Fruit Research Laboratory » Innovative Fruit Production, Improvement, and Protection » Research » Publications at this Location » Publication #345492

Title: Alteration of TAC1 expression in Prunus species leads to pleiotropic shoot phenotypes

item HOLLENDER, COURTNEY - Michigan State University
item Waite, Jessica
item Tabb, Amy
item Raines, Charles - Doug
item Srinivasan, Chinnathambi
item Dardick, Christopher - Chris

Submitted to: Horticulture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2018
Publication Date: 5/1/2018
Citation: Hollender, C., Guseman, J.M., Tabb, A., Raines, C.D., Srinivasan, C., Dardick, C.D. 2018. Alteration of TAC1 expression in Prunus species leads to pleiotropic shoot phenotypes. Horticulture Research.

Interpretive Summary: Tree management including pruning, training, and grafting to rootstocks is the primary cost to growers. Currently, breeding efforts for fruit trees have focused on altered plant architectures that require less management and facilitate high density planting for improved productivity. We previously discovered a gene in vertically growing ‘pillar’ peach trees called TILLER ANGLE CONTROL 1 (TAC1) that controls the angle of branch growth. Here we show that biotechnology strategies can be used to modify TAC1 gene activity to rationally design trees with desirable growth habits. In addition, we show that natural variation in the TAC1 gene appears be associated with more upright growth habits in plum. Lastly, gene expression profiling revealed that TAC1 may function by modifying the profiles or activity of key plant hormones known to be involved in stress and defense signaling. This work has important implications for breeding trees with upright architectures that are highly desired by tree agricultural and ornamental industries.

Technical Abstract: Prunus persica (peach) trees carrying the ‘Pillar’ or ‘Broomy’ trait (br) have vertically oriented branches caused by loss of function mutations in a gene called TILLER ANGLE CONTROL 1 (TAC1). TAC1 encodes a protein in the IGT gene family that includes LAZY1 and DEEPER ROOTING 1 (DRO1), which regulate lateral branch and root orientations, respectively. Here, we found that native TAC1 alleles in the hexaploid plum species Prunus domestica which has a naturally more upright stature contained a variable length trinucleotide repeat within the same exon 3 region previously found to be disrupted in pillar peach trees. RNAi silencing of TAC1 in plum resulted in trees with vertical branch orientations similar to those in pillar peaches but with a narrower profile while PpeTAC1 over-expression led to more horizontal branch angles. Pillar peach trees and transgenic plum lines exhibited inconsistent pleiotropic phenotypes including differences in trunk and branch diameter, stem growth, and twisting branch phenotypes. Expression profiling of pillar peach trees revealed differential expression of numerous genes associated with biotic and abiotic stress, hormone responses, plastids, reactive oxygen, and secondary and cell wall metabolism. Collectively, the data provide important clues for understanding TAC1 function and show that alteration of TAC1 expression may have broad applicability to agricultural and ornamental tree industries.