Abstract
Drought disrupts pollen tube guidance via nitric oxide accumulation at the ovular micropyle, leading to fertilization failure Drought stress increased the relative expression of GhNIAD and NR activity in the ovules of both cotton cultivars, promoting the conversion of NO2- to NO. The reduction in GSNOR activity under drought conditions inhibited the breakdown of GSNO, maintaining higher NO levels in the ovules. Drought stress has been reported to impair chemotropism of pollen tube growth in the pistil, yet the physiological mechanisms underlying this phenomenon remain unexplored in G . hirsutum . This study hypothesized that drought-induced nitric oxide (NO) changes in ovules may inhibit pollen tube directional growth. To test the above hypothesis, pools experiments were conducted using two cotton ( Gossypium hirsutum L.) cultivars Yuzaomian 9110 (drought-sensitive) and Dexiamian 1 (drought-tolerant) under water stress. Results demonstrated that drought stress inhibited the directional growth of pollen tube to the embryo sac and simultaneously reduced fertilization rate, the number of cotton seeds per boll as well as the single boll weight. Moreover, correlation analyses showed that NO content in the ovules had significantly negative correlation with the fertilization rate, implying that NO changes in ovules might inhibit pollen tube directional growth and subsequent yield component formation. Further analyses showed that drought stress elevated nitrate reductase (NR) activity in the ovules of both cultivars, facilitating the conversion of nitrite (NO 2 - ) to NO. This process was accompanied by the up-regulation of NR gene ( GhNIAD ) expressions in the drought-affected ovules of both cultivars, further promoting NO synthesis. The reduction in S-nitrosoglutathione reductase (GSNOR) activity under drought conditions was correlated with an accumulation of S-nitrosoglutathione (GSNO), suggesting that the compromised removal of NO contributed to the higher NO levels in the ovules. Additionally, elevated NO levels may, as part of a regulatory mechanism, further inhibit the activity of GSNOR in the ovules of both cultivars under drought stress. Thus, these findings revealed that drought leads to the accumulation of NO in the cotton ovules, which may be a factor inhibiting pollen tube growth. Of course, this causal relationship requires more evidence to be confirmed in future research. These results provide novel insights into the molecular-physiological mechanisms by which water deficit triggers reproductive failure in cotton.
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Claims 9
Claim · model-written summary
Drought inhibited directional pollen tube growth toward the embryo sac.
- Taxon
- Gossypium hirsutum
Gossypium hirsutumt0 - Organ / stage
- pollen tubee0
- Treatment
- drought stresse0
- Outcome
- directional growth of pollen tube to the embryo sace0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“drought stress inhibited the directional growth of pollen tube to the embryo sac”
t0“Gossypium hirsutum”
t1“Gossypium hirsutum”
Claim · model-written summary
Drought reduced fertilization rate, seed number per boll and boll weight.
- Taxon
- cottonGossypium hirsutume0
- Treatment
- drought stresse0
- Outcome
- fertilization rate, the number of cotton seeds per boll as well as the single boll weighte0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“drought stress inhibited the directional growth of pollen tube to the embryo sac and simultaneously reduced fertilization rate, the number of cotton seeds per boll as well as the single boll weight”
t0“Gossypium hirsutum”
t1“Gossypium hirsutum”
Claim · model-written summary
Ovular NO content was significantly negatively correlated with fertilization rate.
- Taxon
- Gossypium hirsutumGossypium hirsutumt0
- Organ / stage
- ovulese0
- Compound
- NOe0
- Outcome
- fertilization ratee0
- Direction
- negative correlatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NO content in the ovules had significantly negative correlation with the fertilization rate”
t0“Gossypium hirsutum”
t1“Gossypium hirsutum”
Claim · model-written summary
Drought elevated ovular nitrate reductase activity in both cultivars.
- Taxon
- Gossypium hirsutumGossypium hirsutumt0
- Organ / stage
- ovulese0
- Treatment
- drought stresse0
- Gene
- nitrate reductase (NR)e0
- Outcome
- nitrate reductase (NR) activitye0
- Direction
- elevatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“drought stress elevated nitrate reductase (NR) activity in the ovules of both cultivars”
t0“Gossypium hirsutum”
t1“Gossypium hirsutum”
Claim · model-written summary
Drought upregulated GhNIAD expression in ovules of both cultivars.
- Taxon
- Gossypium hirsutumGossypium hirsutumt0
- Organ / stage
- ovulese0
- Treatment
- droughte0
- Gene
- GhNIADe0
- Outcome
- NR gene ( GhNIAD ) expressionse0
- Direction
- up-regulatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“up-regulation of NR gene ( GhNIAD ) expressions in the drought-affected ovules of both cultivars”
t0“Gossypium hirsutum”
t1“Gossypium hirsutum”
Claim · model-written summary
Reduced GSNOR activity under drought correlated with GSNO accumulation.
- Taxon
- Gossypium hirsutumGossypium hirsutumt0
- Gene
- S-nitrosoglutathione reductase (GSNOR)e0
- Compound
- S-nitrosoglutathione (GSNO)e0
- Outcome
- accumulation of S-nitrosoglutathione (GSNO)e0
- Direction
- accumulatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The reduction in S-nitrosoglutathione reductase (GSNOR) activity under drought conditions was correlated with an accumulation of S-nitrosoglutathione (GSNO)”
t0“Gossypium hirsutum”
t1“Gossypium hirsutum”
Claim · model-written summary
Elevated NO may further inhibit GSNOR activity under drought.
- Taxon
- Gossypium hirsutumGossypium hirsutumt0
- Gene
- GSNORe0
- Compound
- NOe0
- Outcome
- activity of GSNORe0
- Direction
- inhibite0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated NO levels may, as part of a regulatory mechanism, further inhibit the activity of GSNOR in the ovules of both cultivars under drought stress”
t0“Gossypium hirsutum”
t1“Gossypium hirsutum”
Claim · model-written summary
Drought led to NO accumulation in cotton ovules.
- Taxon
- cottonGossypium hirsutume0
- Organ / stage
- ovulese0
- Treatment
- droughte0
- Outcome
- accumulation of NOe0
- Direction
- accumulatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“drought leads to the accumulation of NO in the cotton ovules”
t0“Gossypium hirsutum”
t1“Gossypium hirsutum”
Claim · model-written summary
Ovular NO accumulation may inhibit pollen tube growth, but causality remains unconfirmed.
- Taxon
- cottonGossypium hirsutume0
- Compound
- NOe0
- Outcome
- pollen tube growthe0
- Qualifier
- requires more evidencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NO in the cotton ovules, which may be a factor inhibiting pollen tube growth. Of course, this causal relationship requires more evidence”
t0“Gossypium hirsutum”
t1“Gossypium hirsutum”
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