Abstract
Later-flowering spikelets in a rice panicle, referred to as the inferior spikelets, are usually poorly filled and often limit the yield potential of some rice cultivars. The physiological and molecular mechanism for such poor grain filling remains unclear. In this study the differentially expressed genes in starch synthesis and hormone signalling between inferior and superior spikelets were comprehensively analysed and their relationships with grain filling was investigated. DNA microarray and real-time PCR analysis revealed that a group of starch metabolism-related genes showed enhanced expression profiles and had higher transcript levels in superior spikelets than in inferior ones at the early and middle grain-filling stages. Expression of the abscisic acid (ABA) synthesis genes, 9-cis-epoxycarotenoid dioxygenase 1 (NCED1) and NCED5, and the ethylene synthesis genes, 1-aminocyclopropane-1-carboxylate oxidase 1 (ACO1) and ACO3, declined with development of the caryopses. Meanwhile, if compared with inferior spikelets, expression of these genes in superior spikelets decreased faster and had lower transcript profiles, especially for ethylene. ABA concentration and ethylene evolution rate showed similar trends to their gene expression. Exogenous supply of ABA reduced the sucrose synthase (SUS) mRNA level and its enzyme activity in detached rice grains, while exogenously supplied ethephon (an ethylene-releasing reagent) suppressed the expression of most starch synthesis genes; that is, SUS, ADP-glucose pyrophosphorylase (AGPase), and soluble starch synthase (SSS), and down-regulated their enzyme activities. In summary, it is concluded that the relatively high concentrations of ethylene and ABA in inferior spikelets suppress the expression of starch synthesis genes and their enzyme activities and consequently lead to a low grain-filling rate.
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Claims 10
Claim · model-written summary
Starch metabolism genes had higher early and middle grain filling expression in superior spikelets.
- Taxon
- rice
Oryza sativat0 - Organ / stage
- superior spikeletse0
- Gene
- starch metabolism-related genese0
- Outcome
- transcript levelse0
- Direction
- highere0
- Qualifier
- early and middle grain-filling stagese0
- Comparator
- inferior onese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“starch metabolism-related genes showed enhanced expression profiles and had higher transcript levels in superior spikelets than in inferior ones at the early and middle grain-filling stages”
t0“rice inferior and superior spikelets”
Claim · model-written summary
ABA synthesis gene expression declined during caryopsis development.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Expression of the abscisic acid (ABA) synthesis genes, 9-cis-epoxycarotenoid dioxygenase 1 (NCED1) and NCED5, and the ethylene synthesis genes, 1-aminocyclopropane-1-carboxylate oxidase 1 (ACO1) and ACO3, declined with development of the caryopses”
t0“rice inferior and superior spikelets”
Claim · model-written summary
Ethylene synthesis gene expression declined during caryopsis development.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Expression of the abscisic acid (ABA) synthesis genes, 9-cis-epoxycarotenoid dioxygenase 1 (NCED1) and NCED5, and the ethylene synthesis genes, 1-aminocyclopropane-1-carboxylate oxidase 1 (ACO1) and ACO3, declined with development of the caryopses”
t0“rice inferior and superior spikelets”
Claim · model-written summary
These gene expression levels fell faster and lower in superior than inferior spikelets.
- Taxon
- riceOryza sativat0
- Organ / stage
- superior spikeletse0
- Outcome
- transcript profilese0
- Direction
- lowere0
- Qualifier
- especially for ethylenee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“expression of these genes in superior spikelets decreased faster and had lower transcript profiles, especially for ethylene”
t0“rice inferior and superior spikelets”
Claim · model-written summary
ABA concentration followed the expression trend.
- Taxon
- riceOryza sativat0
- Outcome
- ABA concentratione0
- Direction
- similar trendse0
- Comparator
- gene expressione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA concentration and ethylene evolution rate showed similar trends to their gene expression”
t0“rice inferior and superior spikelets”
Claim · model-written summary
Ethylene evolution rate followed the expression trend.
- Taxon
- riceOryza sativat0
- Outcome
- ethylene evolution ratee0
- Direction
- similar trendse0
- Comparator
- gene expressione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA concentration and ethylene evolution rate showed similar trends to their gene expression”
t0“rice inferior and superior spikelets”
Claim · model-written summary
Exogenous ABA reduced SUS mRNA levels and enzyme activity.
- Taxon
- riceOryza sativae0
- Organ / stage
- detached rice grainse0
- Treatment
- Exogenous supply of ABAe0
- Gene
- sucrose synthase (SUS)e0
- Outcome
- mRNA level and its enzyme activitye0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exogenous supply of ABA reduced the sucrose synthase (SUS) mRNA level and its enzyme activity in detached rice grains”
Claim · model-written summary
Ethephon suppressed expression of SUS, AGPase and SSS.
- Taxon
- riceOryza sativat0
- Treatment
- exogenously supplied ethephone0
- Gene
- SUSe0
- Outcome
- expression of most starch synthesis genese0
- Direction
- suppressede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exogenously supplied ethephon (an ethylene-releasing reagent) suppressed the expression of most starch synthesis genes; that is, SUS, ADP-glucose pyrophosphorylase (AGPase), and soluble starch synthase (SSS)”
t0“rice inferior and superior spikelets”
Claim · model-written summary
Ethephon down-regulated starch synthesis enzyme activities.
- Taxon
- riceOryza sativat0
- Treatment
- ethephone1
- Outcome
- enzyme activitiese0
- Direction
- down-regulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“and down-regulated their enzyme activities”
t0“rice inferior and superior spikelets”
e1“exogenously supplied ethephon (an ethylene-releasing reagent)”
Claim · model-written summary
The authors conclude elevated ethylene and ABA suppress starch synthesis in inferior spikelets.
- Taxon
- riceOryza sativat0
- Organ / stage
- inferior spikeletse0
- Compound
- ethylene and ABAe0
- Outcome
- low grain-filling ratee0
- Qualifier
- suppress the expression of starch synthesis genes and their enzyme activitiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“relatively high concentrations of ethylene and ABA in inferior spikelets suppress the expression of starch synthesis genes and their enzyme activities and consequently lead to a low grain-filling rate”
t0“rice inferior and superior spikelets”
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