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Phytochrome gene expression and phylogenetic analysis in the short‐day plant Pharbitis nil (Convolvulaceae): Differential regulation by light and an endogenous clock
Author(s) -
Zheng Cheng Chao,
Potter Daniel,
O'Neill Sharman D.
Publication year - 2009
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.0800340
Subject(s) - phytochrome , biology , pharbitis nil , functional divergence , botany , eudicots , gymnosperm , phylogenetic tree , molecular clock , gene , phytochrome a , gene family , genetics , evolutionary biology , arabidopsis , gene expression , mutant , taxonomy (biology) , red light
To investigate the role of distinct phytochrome pools in photoperiodic timekeeping, we characterized four phytochrome genes in the short‐day plant Pharbitis nil . Each PHY gene had different photosensory properties and sensitivity to night break that inhibits flowering. During extended dark periods, PHYE, PHYB , and PHYC mRNA accumulation exhibited a circadian rhythmicity indicative of control by an endogenous clock. Phylogenetic analysis recovered four clades of angiosperm phytochrome genes, phyA, phyB, phyC , and phyE . All except the phyE clade included sequences from both monocots and eudicots. In addition, phyA is sister to phyC and phyE sister to phyB , with gymnosperm sequences sister to either the phyA ‐ phyC clade or to the phyB ‐ phyE clade. These results suggest that a single duplication occurred in an ancestral seed plant before the divergence of extant gymnosperms from angiosperms and that two subsequent duplications occurred in an ancestral angiosperm before the divergence of monocots from eudicots. Thus in P. nil , a multigene family with different patterns of mRNA abundance in light and darkness contributes to the total phytochrome pool: one pool is light labile ( phyA ), whereas the other is light stable ( phyB and phyE ). In addition, PHYC mRNA represents a third phytochrome pool with intermediate photosensory properties.