Active-type starch synthase (SS) IIa from indica rice partially complements the sugary-1 phenotype in japonica rice endosperm
Key message Introduction of higher SSIIa activity to mild-type isa1 mutant by crossing results in restoration of crystallinity, starch granule structure, and production of plump seeds. Isoamylase 1 (ISA1) removes improper α-1, 6 glycosidic branches of amylopectin generated by starch branching enzyme...
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Published in | Plant molecular biology Vol. 108; no. 4-5; pp. 325 - 342 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Dordrecht
Springer Netherlands
01.03.2022
Springer Springer Nature B.V |
Subjects | |
Online Access | Get full text |
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Summary: | Key message
Introduction of higher SSIIa activity to mild-type
isa1
mutant by crossing results in restoration of crystallinity, starch granule structure, and production of plump seeds.
Isoamylase 1 (ISA1) removes improper α-1, 6 glycosidic branches of amylopectin generated by starch branching enzymes and is essential for the formation of proper amylopectin structure. Rice
isa1
(
sug-1
) mutants in japonica cultivar with less-active starch synthase IIa (SSIIa) and low granule-bound SSI (GBSSI) expression display wrinkled seed phenotype by accumulating water-soluble phytoglycogen instead of insoluble amylopectin. Expression of active SSIIa in transgenic rice produced with a severe-type
isa1
mutant accumulated some insoluble glucan with weak B-type crystallinity at the periphery of seeds but their seeds remained wrinkled. To see whether introduction of high levels of SSIIa and/or GBSSI can restore the grain filling of the mild-type
sug-1
mutant (EM653), new rice lines (
SS2a gbss1
L
isa1
,
ss2a
L
GBSS1 isa1
, and
SS2a GBSS1 isa1
) were generated by crossing japonica
isa1
mutant (
ss2a
L
gbss1
L
isa1
) with wild type indica rice (
SS2a GBSS1 ISA1
). The results showed that
SS2a gbss1
L
isa1
and
SS2a GBSS1 isa1
lines generated chalky plump seeds accumulating insoluble amylopectin-like glucans with an increase in DP 13–35, while
ss2a
L
GBSS1 isa1
generated wrinkly seeds and accumulated soluble glucans enriched with DP < 13. Scanning electron microscopic observation of cross-section of the seeds showed that
SS2a gbss1
L
isa1
and
SS2a GBSS1 isa1
produced wild type-like polygonal starch granules. These starches showed the A-type crystallinity comparable to the wild type, while the japonica
isa1
mutant and the transgenic rice do not show any or little crystallinity, respectively. These results indicate that introduction of higher SSIIa activity can mostly complements the mild-type
sug-1
phenotype. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0167-4412 1573-5028 |
DOI: | 10.1007/s11103-021-01161-9 |