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phyB‐1 sorghum maintains responsiveness to simulated shade, irradiance and red light : far‐red light
Author(s) -
FINLAYSON SCOTT A.,
HAYS DIRK B.,
MORGAN PAGE W.
Publication year - 2007
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2007.01695.x
Subject(s) - phytochrome , elongation , far red , sorghum , mutant , ethylene , biology , shoot , botany , irradiance , biophysics , horticulture , red light , agronomy , gene , optics , materials science , biochemistry , physics , metallurgy , ultimate tensile strength , catalysis
The sorghum [ Sorghum bicolor (L.) Moench] phyB‐1 mutant exhibits a constitutive shade‐avoidance phenotype including excessive shoot elongation. It was previously shown that this mutant also overproduces ethylene. Although phytochrome B (phyB) is assumed to be the pigment most important in sensing and transducing shade signals, the sorghum phyB‐1 mutant still responds to light signals characteristic of shade. Specifically, it was determined that the leaf blade : leaf sheath elongation of phyB‐1 is responsive to red : far red (R : FR), but this response is opposite that of wild type (WT). Reducing the photosynthetic photon flux density (PPFD) strongly reduced the leaf blade : leaf sheath of WT but did not affect phyB‐1 , demonstrating a role for phyB in sensing PPFD. Using light‐emitting diode (LED) lighting, it was found that WT ethylene production was increased with low R : FR while PPFD had no effect. Conversely, phyB‐1 ethylene production increased only with high PPFD, high R : FR which was the treatment resulting in the least ethylene production by WT. Elevated ethylene production inhibits shoot elongation, but may contribute to shade avoidance by reducing leaf blade : leaf sheath elongation. Ethylene responses to light treatments designed to promote or reduce phytochrome A (phyA) activity, and the analysis of PHYA levels in the two cultivars suggests that phyA could be involved in transducing shade signals in light‐grown sorghum. Responses potentially tranduced by phyA are elevated in phyB‐1 which also over‐expresses PHYA.