The identification and characterization of seedlings hyper-responsive to light 2 (SHL2), a gene implicated in developmental responses to light

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Title: The identification and characterization of seedlings hyper-responsive to light 2 (SHL2), a gene implicated in developmental responses to light
Author: Seong, Mi-Seon
Abstract: Mutants showing developmental hyper -responsiveness to limited light were screened and designated as seedlings hyper -responsive to light (shl ) . These mutants showed an etiolated phenotype similar to wild type in the dark , yet had shorter hypocotyls , larger cotyledons , and more advanced development of true leaves than wild type in low light . The SHL genes act (genetically ) as light -dependent negative regulators of photomorphogenesis , possibly in a downstream signaling or developmental pathway that is shared by the major photoreceptor genes (CRY1 , PHYA , and PHYB ) and other photoreceptors (CRY2 , PHYC , PHYD , and PHYE ) . shl1 and shl2 were shown to be partially dependent on HY5 activity for their light -hyperresponsive phenotypes . shl1 -1 showed a defect in responding to auxin in its root development in both white and yellow light conditions , and showed a defect in responding to auxin in hypocotyl elongation in yellow light . Compared to wild type , both shl1 -1 and shl2 -2 showed increased hypocotyl length in response to cytokinin in white light . Gibberellin (GA ) partially recovered shl1 -1 mutant phenotype in yellow light , whereas showed no effect on hypocotyl elongation of shl2 -2 in this light condition . These altered responses of shl1 -1 and shl2 -2 to multiple phytohormones in different light regimes suggests that cross -talks among light and hormones regulate SHL1 and SHL2 . One of the SHL genes , SHL2 was cloned by map -based positional cloning and shown to be allelic to the previously identified locus designated murus3 (mur3 ) and katamari1 (kam1 ) . MUR3 /KAM1 encodes a XyG galactosyltransferase . Sequence analysis demonstrated that our original EMS generated reference allele shl2 -2 is probably not a null mutant , therefore the phenotypes of T -DNA insertion null mutant in SHL2 , SALK _074435 were studied in different light conditions . Unlike shl2 -2 , SALK _074435 had a slightly short hypocotyl phenotype in the dark (though not to the extent of the det /cop /fus mutants ) . A consideration of the phenotypes and molecular lesions of shl2 -2 and mur3 alleles , along with the phenotypes of null alleles kam1 and SALK _74435 , suggests that SHL2 /MUR3 /KAM1 may be involved in hypocotyl elongation in low light through the modification of xyloglucan in the plant cell wall , and may play a role in hypocotyl elongation in the dark through proper organization of the endomembrane .
URI: http : / /hdl .handle .net /1969 .1 /4764
Date: 2007-04-25

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The identification and characterization of seedlings hyper-responsive to light 2 (SHL2), a gene implicated in developmental responses to light. Available electronically from http : / /hdl .handle .net /1969 .1 /4764 .

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