Abstract
To identify potential regulators of photoassimilate partitioning, we screened for rice mutant plants that accumulate high levels of starch in the leaf blades, and a mutant line leaf starch excess 1 (LSE1) was obtained and characterized. The starch content in the leaf blades of LSE1 was more than 10-fold higher than that in wild-type plants throughout the day, while the sucrose content was unaffected. The gene responsible for the LSE1 phenotype was identified by gene mapping to be a gene encoding α-glucan water dikinase, OsGWD1 (Os06g0498400), and a 3.4-kb deletion of the gene was found in the mutant plant. Despite the hyperaccumulation of starch in their leaf blades, LSE1 plants exhibited no significant change in vegetative growth, presenting a clear contrast to the reported mutants of Arabidopsis thaliana and Lotus japonicus in which disruption of the genes for α-glucan water dikinase leads to marked inhibition of vegetative growth. In reproductive growth, however, LSE1 exhibited fewer panicles per plant, lower percentage of ripened grains and smaller grains; consequently, the grain yield was lower in LSE1 plants than in wild-type plants by 20~40%. Collectively, although α-glucan water dikinase was suggested to have universal importance in leaf starch degradation in higher plants, the physiological priority of leaf starch in photoassimilate allocation may vary among plant species.
Highlights
Assimilate partitioning has long been recognized as a target for crop improvement because it can limit the yield potential of the crop plants
We used the progeny of the two putative homozygous mutant plants as the pure line for the mutation and designated this mutation leaf starch excess 1 (LSE1), while the progeny of the two putative wild-type genotype plants were used as controls in the various assays in this study and were designated “wild-type.”
We examined whether the structure of the OsGWD1 gene was different between the LSE1 mutant and the original cultivar Nipponbare, by genomic polymerase chain reaction (PCR) analysis using several primer combinations designed based on the published DNA sequence of Os06g0498400
Summary
Assimilate partitioning has long been recognized as a target for crop improvement because it can limit the yield potential of the crop plants. Starch excess in the leaves is often observed when any inhibition occurs (1) in the export of photoassimilate from source leaves or (2) in starch metabolism in the leaves. The former case includes disruption or suppression of the phloem-loading sucrose transporter (Bürkle et al, 1998; Gottwald et al, 2000) and blockade of the route of assimilate transport (Russin et al, 1996). As is clear from the above described examples, the study of mutant plants exhibiting the starch excess phenotype in their leaves is a good approach to acquiring a better understanding of the mechanisms and regulation of photoassimilate allocation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
