Abstract
The phytohormone cytokinin (CK) is known to delay senescence in plants. We studied the effect of a CK analog, 6-benzyl adenine (BA), on rice leaves to understand the possible mechanism by which CK delays senescence in a drought- and heat-tolerant rice cultivar Nagina22 (N22) using dark-induced senescence (DIS) as a surrogate for natural senescence of leaves. Leaves of N22-H-dgl162, a stay-green mutant of N22, and BA-treated N22 showed retention of chlorophyll (Chl) pigments, maintenance of the Chl a/b ratio, and delay in reduction of both photochemical efficiency and rate of oxygen evolution during DIS. HPLC analysis showed accumulation of 7-hydroxymethyl chlorophyll (HmChl) during DIS, and the kinetics of its accumulation correlated with progression of senescence. Transcriptome analysis revealed that several plastid-localized genes, specifically those associated with photosystem II (PSII), showed higher transcript levels in BA-treated N22 and the stay-green mutant leaves compared with naturally senescing N22 leaves. Real-time PCR analyses showed that genes coding for enzymes associated with Chl a/b interconversion and proteins associated with light-harvesting complexes maintained higher transcript levels up to 72h of DIS following BA treatment. The pigment-protein complexes analyzed by green gel remained intact in both N22-H-dgl162 and BA-treated N22 leaves even after 96h of DIS. Thus, CK delays senescence by accumulation of HmChl and up-regulating genes in the Chl cycle, thereby maintaining the Chl a/b ratio. Also, CK treatment retains higher transcript levels of PSII-related genes, resulting in the stability of photosynthetic pigment complexes and functional stay-greenness in rice.
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Claims 9
Claim · model-written summary
BA-treated N22 and the stay-green mutant retained more chlorophyll during dark-induced senescence.
- Taxon
- rice
Oryza sativat0 - Material
- N22-H-dgl162e1
- Treatment
- BA-treated N22e1
- Outcome
- chlorophyll (Chl) pigmentse1
- Direction
- increaseinferrede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“delays dark-induced senescence in rice”
e1“Leaves of N22-H-dgl162, a stay-green mutant of N22, and BA-treated N22 showed retention of chlorophyll (Chl) pigments, maintenance of the Chl a/b ratio, and delay in reduction of both photochemical efficiency and rate of oxygen evolution during DIS”
Claim · model-written summary
BA-treated N22 and the stay-green mutant delayed the reduction of photochemical efficiency and oxygen evolution during dark-induced senescence.
- Taxon
- riceOryza sativat0
- Material
- N22-H-dgl162e1
- Treatment
- BA-treated N22e1
- Outcome
- photochemical efficiency and rate of oxygen evolutione1
- Direction
- delay in reductione1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“delays dark-induced senescence in rice”
e1“Leaves of N22-H-dgl162, a stay-green mutant of N22, and BA-treated N22 showed retention of chlorophyll (Chl) pigments, maintenance of the Chl a/b ratio, and delay in reduction of both photochemical efficiency and rate of oxygen evolution during DIS”
Claim · model-written summary
BA-treated N22 and the stay-green mutant maintained the chlorophyll a/b ratio during dark-induced senescence.
- Taxon
- riceOryza sativat0
- Material
- N22-H-dgl162e1
- Treatment
- BA-treated N22e1
- Outcome
- Chl a/b ratioe1
- Direction
- no_changeinferrede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“delays dark-induced senescence in rice”
e1“Leaves of N22-H-dgl162, a stay-green mutant of N22, and BA-treated N22 showed retention of chlorophyll (Chl) pigments, maintenance of the Chl a/b ratio, and delay in reduction of both photochemical efficiency and rate of oxygen evolution during DIS”
Claim · model-written summary
Accumulation of 7-hydroxymethyl chlorophyll (HmChl) correlated with the progression of senescence.
- Taxon
- riceOryza sativat0
- Compound
- 7-hydroxymethyl chlorophyll (HmChl)e2
- Outcome
- kinetics of its accumulatione2
- Direction
- increaseinferrede2
- Qualifier
- correlated with progression of senescencee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“delays dark-induced senescence in rice”
e2“HPLC analysis showed accumulation of 7-hydroxymethyl chlorophyll (HmChl) during DIS, and the kinetics of its accumulation correlated with progression of senescence”
Claim · model-written summary
BA-treated N22 and the stay-green mutant leaves had higher transcript levels of photosystem II-associated plastid genes than naturally senescing N22 leaves.
- Taxon
- riceOryza sativat0
- Material
- stay-green mutante3
- Organ / stage
- leavese3
- Treatment
- BA-treated N22e3
- Outcome
- plastid-localized genes, specifically those associated with photosystem II (PSII)e3
- Direction
- highere3
- Comparator
- naturally senescing N22 leavese3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“delays dark-induced senescence in rice”
e3“several plastid-localized genes, specifically those associated with photosystem II (PSII), showed higher transcript levels in BA-treated N22 and the stay-green mutant leaves compared with naturally senescing N22 leaves”
Claim · model-written summary
BA treatment maintained higher transcript levels of Chl a/b interconversion enzyme and light-harvesting genes up to 72 h of dark-induced senescence.
- Taxon
- riceOryza sativat0
- Treatment
- BA treatmente4
- Outcome
- genes coding for enzymes associated with Chl a/b interconversione4
- Direction
- highere4
- Qualifier
- up to 72h of DISe4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“delays dark-induced senescence in rice”
e4“genes coding for enzymes associated with Chl a/b interconversion and proteins associated with light-harvesting complexes maintained higher transcript levels up to 72h of DIS following BA treatment”
Claim · model-written summary
Pigment-protein complexes remained intact in N22-H-dgl162 and BA-treated N22 after 96 h of dark-induced senescence.
- Taxon
- riceOryza sativat0
- Material
- N22-H-dgl162e5
- Treatment
- BA-treated N22e5
- Outcome
- pigment-protein complexese5
- Qualifier
- after 96h of DISe5
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“delays dark-induced senescence in rice”
e5“The pigment-protein complexes analyzed by green gel remained intact in both N22-H-dgl162 and BA-treated N22 leaves even after 96h of DIS”
Claim · model-written summary
Cytokinin delays senescence by accumulating HmChl and up-regulating chlorophyll cycle genes, which maintains the chlorophyll a/b ratio.
- Taxon
- riceOryza sativat0
- Treatment
- CKe6
- Compound
- HmChle6
- Outcome
- delays senescencee6
- Qualifier
- up-regulating genes in the Chl cyclee6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“delays dark-induced senescence in rice”
e6“Thus, CK delays senescence by accumulation of HmChl and up-regulating genes in the Chl cycle, thereby maintaining the Chl a/b ratio”
Claim · model-written summary
CK treatment keeps PSII-related gene transcripts high, stabilising photosynthetic pigment complexes and functional stay-greenness in rice.
- Taxon
- riceOryza sativat0
- Treatment
- CK treatmente7
- Gene
- PSII-related genese7
- Outcome
- stability of photosynthetic pigment complexese7
- Qualifier
- functional stay-greennesse7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“delays dark-induced senescence in rice”
e7“CK treatment retains higher transcript levels of PSII-related genes, resulting in the stability of photosynthetic pigment complexes and functional stay-greenness in rice”
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