Abstract
PIN-FORMED (PIN) encodes a key auxin polar transport family that plays a crucial role in the outward transport of auxin and several growth and development processes, including dwarfing trees. We identified a dwarfing pear rootstock ‘OHF51’ (Pyrus communis), which limits the growth vigor of the ‘Xueqing’ (Pyrus bretschneideri × Pyrus pyrifolia) scion, and isolated 14 putative PbPINs from the pear Pyrus bretschneideri. The phylogenic relationships, structure, promoter regions, and expression patterns were analyzed. PbPINs were classified into two main groups based on the protein domain structure and categorized into three major groups using the neighbor-joining algorithm. Promoter analysis demonstrated that PbPINs might be closely related to plant growth and development. Through quantitative real-time PCR (qRT-PCR) analysis, we found that the expression patterns of 14 PbPINs varied upon exposure to different organs in dwarfing and vigorous stocks, ‘OHF51’ and ‘QN101’ (Pyrus betulifolia), indicating that they might play varying roles in different tissues and participated in the regulation of growth vigor. These results provide fundamental insights into the characteristics and evolution of the PINs family, as well as the possible relationship between dwarfing ability and auxin polar transport.
Highlights
Dwarfing and high plant population density are the inevitable trends of fruit production owing to their important features such as earlier fruiting, higher yields, and ease of management
It has been reported that the content, transport, and signaling of hormones might play roles in rootstock/interstock-induced dwarfing
It has been reported that the contents, transport, and signaling of hormones may play roles in rootstock/interstock-induced dwarfing [9,10,11,12,13]
Summary
Dwarfing and high plant population density are the inevitable trends of fruit production owing to their important features such as earlier fruiting, higher yields, and ease of management. Application of growth-regulating agents is sometimes used to control tree vegetative growth [1,2,3,4] and many dwarfing rootstocks or interstocks of fruit trees are widely used to control tree size [5,6,7,8]. Despite its broad utility and the availability of related research on dwarfing rootstocks/interstocks, the underlying mechanism of rootstock/interstock-induced dwarfing is still unknown. It has been suggested that the dwarfing physiological mechanism might be related to the vessel dimensions, hormone metabolism, and phenol contents of rootstocks [9], as well as the disorder of vascular organization reestablishment and the resultant decline in material transport capacity in the graft union. It has been reported that the content, transport, and signaling of hormones might play roles in rootstock/interstock-induced dwarfing.
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