title: ABI3 controls embryo degreening through Mendel's I locus.
abstract: Chlorophyll (chl) is essential for light capture and is the starting point that provides the energy for photosynthesis and thus plant growth. Obviously, for this reason, retention of the green chlorophyll pigment is considered a desirable crop trait. However, the presence of chlorophyll in mature seeds can be an undesirable trait that can affect seed maturation, seed oil quality, and meal quality. Occurrence of mature green seeds in oil crops such as canola and soybean due to unfavorable weather conditions during seed maturity is known to cause severe losses in revenue. One recently identified candidate that controls the chlorophyll degradation machinery is the stay-green gene, SGR1 that was mapped to Mendel's I locus responsible for cotyledon color (yellow versus green) in peas. A defect in SGR1 leads to leaf stay-green phenotypes in Arabidopsis and rice, but the role of SGR1 in seed degreening and the signaling machinery that converges on SGR1 have remained elusive. To decipher the gene regulatory network that controls degreening in Arabidopsis, we have used an embryo stay-green mutant to demonstrate that embryo degreening is achieved by the SGR family and that this whole process is regulated by the phytohormone abscisic acid (ABA) through ABSCISIC ACID INSENSITIVE 3 (ABI3); a B3 domain transcription factor that has a highly conserved and essential role in seed maturation, conferring desiccation tolerance. Misexpression of ABI3 was sufficient to rescue cold-induced green seed phenotype in Arabidopsis. This finding reveals a mechanistic role for ABI3 during seed degreening and thus targeting of this pathway could provide a solution to the green seed problem in various oil-seed crops.
authors.affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada M5S 3B2.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Delmas
authors.forename: Subramanian
authors.initials: S
authors.lastname: Sankaranarayanan
authors.forename: Srijani
authors.initials: S
authors.lastname: Deb
authors.forename: Ellen
authors.initials: E
authors.lastname: Widdup
authors.forename: Céline
authors.initials: C
authors.lastname: Bournonville
authors.forename: Norbert
authors.initials: N
authors.lastname: Bollier
authors.forename: Julian G B
authors.initials: JG
authors.lastname: Northey
authors.forename: Peter
authors.initials: P
authors.lastname: McCourt
authors.forename: Marcus A
authors.initials: MA
authors.lastname: Samuel
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002734:Chlorophyll / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D053263:Gene Regulatory Networks / Q000235:genetics*; D005816:Genetic Complementation Test; D005838:Genotype; D046228:Microarray Analysis; D016254:Mutagenesis, Insertional; D010740:Phospholipases / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000378:metabolism*; D014026:Nicotiana; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: C091601:ABI3 protein, Arabidopsis; D029681:Arabidopsis Proteins; D014157:Transcription Factors; D002734:Chlorophyll; D010740:Phospholipases; C455511:SGR2 phospholipase, Arabidopsis
keywords: freezing tolerance; nondormant
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