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Two B‐box proteins, PpBBX18 and PpBBX21, antagonistically regulate anthocyanin biosynthesis via competitive association with Pyrus pyrifolia ELONGATED HYPOCOTYL 5 in the peel of pear fruit
Author(s) -
Bai Songling,
Tao Ruiyan,
Yin Lei,
Ni Junbei,
Yang Qinsong,
Yan Xinhui,
Yang Feng,
Guo Xianping,
Li Hongxu,
Teng Yuanwen
Publication year - 2019
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.14510
Subject(s) - pear , anthocyanin , hypocotyl , biosynthesis , arabidopsis , transcription factor , biology , biochemistry , gene , activator (genetics) , microbiology and biotechnology , botany , mutant
Summary Light is indispensable for the accumulation of anthocyanin in the peel of red pear fruit ( Pyrus pyrifolia Nakai). ELONGATED HYPOCOTYL 5 (HY5) is considered to be a critical regulator for induction of anthocyanin biosynthesis, but detailed characterization of its regulatory mechanism is needed. In this study, multiple genetic and biochemical approaches were applied to identify the roles of P. pyrifolia HY5 (PpHY5) and two B‐box (BBX) proteins, PpBBX18 and PpBBX21, in the transcriptional regulation of PpMYB10 . The functions of the two BBX proteins were analyzed in overexpression lines using pear calli‐based approaches. On its own PpHY5 was unable to activate downstream genes. The two BBX proteins, PpBBX18 and PpBBX21, physically interacted with PpHY5 and antagonistically regulated anthocyanin biosynthesis in Arabidopsis and pear. PpBBX18 formed a heterodimer with PpHY5 via two B‐box domains, in which PpHY5 bound to the G‐box motif of PpMYB10 and PpBBX18 provided the trans ‐acting activity, thus inducing transcription of PpMYB10 . PpBBX21 interacted with PpHY5 and PpBBX18 and hampered formation of the PpHY5–PpBBX18 active transcription activator complex, and subsequently repressed anthocyanin biosynthesis. The present results demonstrate the fine‐tuned regulation of anthocyanin biosynthesis via transcriptional regulation of PpMYB10 by PpHY5‐associated proteins and provide insights into light‐induced anthocyanin biosynthesis.