Abstract
Certain litchi varieties, such as “Nuomici”, are highly susceptible to preharvest fruit drop, which leads to significant losses in fruit yield and economic value. However, the precise molecular mechanisms underlying this issue are not yet fully understood. In this study, we aimed to elucidate the signaling pathways that facilitate preharvest fruit drop in litchi, using “Nuomici” and “Huaizhi” cultivars as examples, which demonstrate high and low preharvest fruit drop rates, respectively. Our findings revealed that “Nuomici” experienced a substantial preharvest fruit drop, with a cumulative rate of 41.68%, significantly higher than the 1.44% observed in “Huaizhi”. Cellulase activity assays showed a significant increase in cellulase activity in the abscission zone of “Nuomici”, which coincided with the occurrence of preharvest fruit drop, in contrast to the relatively low levels in “Huaizhi”. Phytohormone assays indicated lower indole-3-acetic acid content in the pericarp, aril, and seeds of “Nuomici” during the preharvest stage compared to “Huaizhi”, coupled with higher abscisic acid levels in the seeds of “Nuomici”. Furthermore, transcriptomic analysis identified 180, 282, 655, and 241 differentially expressed genes (DEGs) in the pericarp, aril, seed, and abscission zone, respectively, between the two cultivars during preharvest fruit drop. These DEGs are intricately involved in the generation and transmission of abscission signals from fruit tissues, encompassing PIN , PIN-LIKES , LAX , and SAUR genes related to polar auxin transport, ethylene diffusion, as well as perceiving these signals and activating the abscission process within the abscission zone. This includes ACO and ILR genes involved in hormone biosynthesis and signal transduction, regulation by WRKY, NAC, and bHLH transcription factors, AAO genes involved in response to reactive oxygen species, and EXP, EG, and PG genes involved in cell wall degradation in the abscission zone. Based on these comprehensive findings, we propose a model for preharvest fruit drop triggered by a series of molecular events in litchi, providing valuable insights into the complex mechanisms governing this phenomenon.
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Claims 15
Claim · model-written summary
Nuomici had 41.68% cumulative fruit drop versus 1.44% in Huaizhi.
- Material
- “Nuomici”e0
- Outcome
- preharvest fruit drope0
- Direction
- highere0
- Value
- 41.68%e0
- Qualifier
- 1.44%e0
- Comparator
- “Huaizhi”e0
Not reportedTaxon
Verbatim
e0““Nuomici” experienced a substantial preharvest fruit drop, with a cumulative rate of 41.68%, significantly higher than the 1.44% observed in “Huaizhi””
Claim · model-written summary
Cellulase activity rose in the Nuomici abscission zone as fruit drop occurred, compared with Huaizhi.
- Material
- “Nuomici”e0
- Organ / stage
- abscission zonee0
- Gene
- cellulasee0
- Outcome
- cellulase activitye0
- Direction
- increasee0
- Comparator
- “Huaizhi”e0
Not reportedTaxon
Verbatim
e0“significant increase in cellulase activity in the abscission zone of “Nuomici”, which coincided with the occurrence of preharvest fruit drop, in contrast to the relatively low levels in “Huaizhi””
Claim · model-written summary
Nuomici pericarp had lower indole-3-acetic acid content than Huaizhi before harvest.
- Material
- “Nuomici”e0
- Organ / stage
- pericarpe0
- Outcome
- indole-3-acetic acid contente0
- Direction
- lowere0
- Comparator
- “Huaizhi”e0
Not reportedTaxon
Verbatim
e0“lower indole-3-acetic acid content in the pericarp, aril, and seeds of “Nuomici” during the preharvest stage compared to “Huaizhi””
Claim · model-written summary
Nuomici aril had lower indole-3-acetic acid content than Huaizhi before harvest.
- Material
- “Nuomici”e0
- Organ / stage
- arile0
- Outcome
- indole-3-acetic acid contente0
- Direction
- lowere0
- Comparator
- “Huaizhi”e0
Not reportedTaxon
Verbatim
e0“lower indole-3-acetic acid content in the pericarp, aril, and seeds of “Nuomici” during the preharvest stage compared to “Huaizhi””
Claim · model-written summary
Nuomici seeds had lower indole-3-acetic acid content than Huaizhi before harvest.
- Material
- “Nuomici”e0
- Organ / stage
- seedse0
- Outcome
- indole-3-acetic acid contente0
- Direction
- lowere0
- Comparator
- “Huaizhi”e0
Not reportedTaxon
Verbatim
e0“lower indole-3-acetic acid content in the pericarp, aril, and seeds of “Nuomici” during the preharvest stage compared to “Huaizhi””
Claim · model-written summary
Nuomici seeds had higher abscisic acid levels than Huaizhi.
Not reportedTaxon
Verbatim
e0“higher abscisic acid levels in the seeds of “Nuomici””
Claim · model-written summary
Pericarp had 180 differentially expressed genes between cultivars.
Not reportedTaxon
Verbatim
e0“identified 180, 282, 655, and 241 differentially expressed genes (DEGs) in the pericarp, aril, seed, and abscission zone, respectively”
Claim · model-written summary
Aril had 282 differentially expressed genes between cultivars.
Not reportedTaxon
Verbatim
e0“identified 180, 282, 655, and 241 differentially expressed genes (DEGs) in the pericarp, aril, seed, and abscission zone, respectively”
Claim · model-written summary
Seed had 655 differentially expressed genes between cultivars.
Not reportedTaxon
Verbatim
e0“identified 180, 282, 655, and 241 differentially expressed genes (DEGs) in the pericarp, aril, seed, and abscission zone, respectively”
Claim · model-written summary
Abscission zone had 241 differentially expressed genes between cultivars.
Not reportedTaxon
Verbatim
e0“identified 180, 282, 655, and 241 differentially expressed genes (DEGs) in the pericarp, aril, seed, and abscission zone, respectively”
Claim · model-written summary
PIN, PIN-LIKES, LAX and SAUR genes were implicated in polar auxin transport and abscission signaling.
Not reportedTaxon
Verbatim
e0“PIN , PIN-LIKES , LAX , and SAUR genes related to polar auxin transport”
Claim · model-written summary
ACO and ILR genes were implicated in hormone biosynthesis and signaling.
Not reportedTaxon
Verbatim
e0“ACO and ILR genes involved in hormone biosynthesis and signal transduction”
Claim · model-written summary
WRKY, NAC and bHLH transcription factors were implicated in abscission regulation.
Not reportedTaxon
Verbatim
e0“regulation by WRKY, NAC, and bHLH transcription factors”
Claim · model-written summary
AAO genes were implicated in reactive oxygen species response.
Not reportedTaxon
Verbatim
e0“AAO genes involved in response to reactive oxygen species”
Claim · model-written summary
EXP, EG and PG genes were implicated in cell wall degradation in the abscission zone.
Not reportedTaxon
Verbatim
e0“EXP, EG, and PG genes involved in cell wall degradation in the abscission zone”