Transcriptomics of Improved Fruit Retention by Hexanal in ‘Honeycrisp’ Reveals Hormonal Crosstalk and Reduced Cell Wall Degradation in the Fruit Abscission Zone

Apples (Malus domestica Borkh) are prone to preharvest fruit drop, which is more pronounced in ‘Honeycrisp’. Hexanal is known to improve fruit retention in several economically important crops. The effects of hexanal on the fruit retention of ‘Honeycrisp’ apples were assessed using physiological, biochemical, and transcriptomic approaches. Fruit retention and fruit firmness were significantly improved by hexanal, while sugars and fresh weight did not show a significant change in response to hexanal treatment. At commercial maturity, abscisic acid and melatonin levels were significantly lower in the treated fruit abscission zone (FAZ) compared to control. At this stage, a total of 726 differentially expressed genes (DEGs) were identified between treated and control FAZ. Functional classification of the DEGs showed that hexanal downregulated ethylene biosynthesis genes, such as S-adenosylmethionine synthase (SAM2) and 1-aminocyclopropane-1-carboxylic acid oxidases (ACO3, ACO4, and ACO4-like), while it upregulated the receptor genes ETR2 and ERS1. Genes related to ABA biosynthesis (FDPS and CLE25) were also downregulated. On the contrary, key genes involved in gibberellic acid biosynthesis (GA20OX-like and KO) were upregulated. Further, hexanal downregulated the expression of genes related to cell wall degrading enzymes, such as polygalacturonase (PG1), glucanases (endo-β-1,4-glucanase), and expansins (EXPA1-like, EXPA6, EXPA8, EXPA10-like, EXPA16-like). Our findings reveal that hexanal reduced the sensitivity of FAZ cells to ethylene and ABA. Simultaneously, hexanal maintained the cell wall integrity of FAZ cells by regulating genes involved in cell wall modifications. Thus, delayed fruit abscission by hexanal is most likely achieved by minimizing ABA through an ethylene-dependent mechanism.

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Transcriptomics of improved fruit retention by hexanal in 'Honeycrisp' reveals hormonal crosstalk and reduced cell-wall remodelling in the fruit-abscission zone

10.1101/2021.05.19.444856 ◽

2021 ◽

Author(s):

Karthika Sriskantharajah ◽

Walid El Kayal ◽

Davoud Torkamaneh ◽

Murali Mohan Ayyanath ◽

Praveen K Saxena ◽

...

Keyword(s):

Cell Wall ◽

Molecular Mechanisms ◽

Ethylene Biosynthesis ◽

Abscission Zone ◽

Fruit Abscission ◽

Fruit Drop ◽

Expression Of Genes ◽

Commercial Harvest ◽

Hormonal Crosstalk ◽

Aba Biosynthesis

Apples (Malus domestica Borkh) are prone to pre-harvest fruit drop which is more pronounced in 'Honeycrisp'. Using a transcriptomic approach, we analyzed the molecular mechanisms of fruit retention in 'Honeycrisp'. A total of 726 differentially expressed genes (DEGs) were identified in the abscission zone of hexanal-treated and untreated fruit (FAZ). Hexanal down-regulated the genes involved in ethylene biosynthesis, such as S-adenosylmethionine synthase (SAM2) and 1-aminocyclopropane-1carboxylic acid oxidases (ACO3, ACO4 and ACO4-like). Genes related to ABA biosynthesis (FDPS and CLE25) were also down-regulated. On the contrary, gibberellic acid (GA) biosynthesis genes, gibberellin 20 oxidase1-like (GA20OX-like) and ent-kaurene oxidase (KO) were up-regulated. Further, hexanal down-regulated the expression of genes related to cell-wall remodelling enzymes such as polygalacturonase (PG1), glucanases (endo-β-1,4-glucanase; EG) and expansins (EXPA1-like, EXPA6, EXPA8, EXPA10-like, EXPA16-like). Hexanal also reduced ethylene, and abscisic acid (ABA) production at commercial harvest stage. Hexanal reduced ethylene production in fruits and thus reduced the sensitivity of FAZ cells to ethylene and ABA. Simultaneously, hexanal maintained the cell-wall integrity of FAZ cells by regulating genes involved in cell-wall modifications. Our findings show that fruit abscission is delayed by hexanal, by down regulating ABA through an ethylene-dependent mechanism.

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Aminoethoxyvinylglycine Inhibits Fruit Abscission Induced by Naphthaleneacetic Acid and Associated Relationships with Expression of Genes for Ethylene Biosynthesis, Perception, and Cell Wall Degradation in ‘Delicious’ Apples

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.133.6.727 ◽

2008 ◽

Vol 133 (6) ◽

pp. 727-734 ◽

Cited By ~ 7

Author(s):

Hong Zhu ◽

Eric P. Beers ◽

Rongcai Yuan

Keyword(s):

Cell Wall ◽

Ethylene Production ◽

Acc Oxidase ◽

Ethylene Biosynthesis ◽

Naphthaleneacetic Acid ◽

Cell Wall Degradation ◽

Oxidase Gene ◽

Young Fruit ◽

Fruit Abscission ◽

Expression Of Genes

Effects of naphthaleneacetic acid (NAA) and aminoethoxyvinylglycine (AVG) on young fruit abscission, leaf and fruit ethylene production, and expression of genes related to ethylene biosynthesis and cell wall degradation were examined in ‘Delicious’ apples (Malus ×domestica Borkh.). NAA at 15 mg·L−1 increased fruit abscission and ethylene production of leaves and fruit when applied at the 11-mm stage of fruit development, whereas AVG, an inhibitor of ethylene biosynthesis, at 250 mg·L−1 reduced NAA-induced fruit abscission and ethylene production of leaves and fruit. NAA also increased expression of 1-aminocyclopropane-1-carboxylate (ACC) synthase genes (MdACS5A and MdACS5B), ACC oxidase gene (MdACO1), and ethylene receptor genes (MdETR1a, MdETR1b, MdETR2, MdERS1, and MdERS2) in fruit cortex and fruit abscission zones. However, AVG reduced NAA-induced expression of these genes except for MdERS2 in fruit abscission zones. NAA increased expression of the polygalacturonase gene MdPG2 in fruit abscission zones but not in fruit cortex, whereas AVG reduced NAA-enhanced expression of MdPG2 in fruit abscission zones. The expression of β-1,4-glucanase gene MdCel1 in fruit abscission zones was decreased by NAA but was unaffected by AVG. Our results suggest that ethylene biosynthesis, ethylene perception, and the MdPG2 gene are involved in young fruit abscission caused by NAA.

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Effects of 1-Methylcyclopropene and Naphthaleneacetic Acid on Fruit Set and Expression of Genes Related to Ethylene Biosynthesis and Perception and Cell Wall Degradation in Apple

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.135.5.402 ◽

2010 ◽

Vol 135 (5) ◽

pp. 402-409 ◽

Cited By ~ 13

Author(s):

Hong Zhu ◽

Rongcai Yuan ◽

Duane W. Greene ◽

Eric P. Beers

Keyword(s):

Cell Wall ◽

Fruit Set ◽

Ethylene Biosynthesis ◽

Apple Fruit ◽

Naphthaleneacetic Acid ◽

Cell Wall Degradation ◽

Fruit Abscission ◽

Expression Of Genes ◽

Small Influence ◽

Negative Effect

The effects of 1-methylcyclopropene (1-MCP) and naphthaleneacetic acid (NAA) on fruit set and the expression of genes related to ethylene biosynthesis and perception and cell wall degradation in apple (Malus ×domestica Borkh.) were studied when applied during the normal chemical thinning period. 1-MCP at 209 mg·L−1 had a small negative effect or no effect on the final fruit set, depending on the experiment, but could cause a transient delay of June drop when applied at petal fall or the 10-mm stage in ‘Pioneer McIntosh’ apple. 1-MCP at 160 mg·L−1 had no effect on fruit abscission but induced ethylene production by leaves and fruit of ‘Golden Delicious’ apple. NAA at 6 or 15 mg·L−1 effectively increased fruit abscission in both apple cultivars. NAA enhanced the expression of genes related to ethylene biosynthesis (MdACS5A, MdACS5B, and MdACO1) or perception (MdETR1, MdETR1b, MdETR2, MdERS1, and MdERS2) and cell wall degradation (MdPG2). 1-MCP did not affect the expression of MdACS5A and MdACS5B in the fruit abscission zone (FAZ), although it enhanced the expression of these two genes in the fruit cortex (FC) from 6 hours to 1 day after treatment. The expression of MdACO1 in both tissues was increased by 1-MCP by 3 days post-treatment and thereafter. 1-MCP had only a small influence on the expression of most ethylene receptor genes, with the exception of MdETR1, which was upregulated in the FC to a level similar to that observed for NAA treatment. In response to 1-MCP, in the FAZ, the expression of MdCel1 and MdPG2 was upregulated at the beginning and the end, respectively, of the experiment, but otherwise remained at or below control levels. 1-MCP did not inhibit NAA-induced abscission of young apple fruit, suggesting that abscission does not solely depend on ethylene signal transduction, or that the periods of effectiveness for 1-MCP and ethylene were asynchronous.

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NAA and Ethylene Regulate Expression of Genes Related to Ethylene Biosynthesis, Perception, and Cell Wall Degradation During Fruit Abscission and Ripening in ‘Delicious’ Apples

Journal of Plant Growth Regulation ◽

10.1007/s00344-008-9055-6 ◽

2008 ◽

Vol 27 (3) ◽

pp. 283-295 ◽

Cited By ~ 52

Author(s):

Jianguo Li ◽

Rongcai Yuan

Keyword(s):

Cell Wall ◽

Ethylene Biosynthesis ◽

Cell Wall Degradation ◽

Fruit Abscission ◽

Expression Of Genes

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Profiling the Expression of Genes Related to Ethylene Biosynthesis, Ethylene Perception, and Cell Wall Degradation during Fruit Abscission and Fruit Ripening in Apple

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.135.5.391 ◽

2010 ◽

Vol 135 (5) ◽

pp. 391-401 ◽

Cited By ~ 14

Author(s):

Jianguo Li ◽

Hong Zhu ◽

Rongcai Yuan

Keyword(s):

Cell Wall ◽

Fruit Ripening ◽

Ethylene Biosynthesis ◽

Fruit Softening ◽

Cell Wall Degradation ◽

Oxidase Gene ◽

Transcript Levels ◽

Fruit Abscission ◽

Expression Of Genes ◽

Golden Delicious

The expression of genes for ethylene biosynthesis, ethylene perception, and cell wall degradation in the fruit cortex and fruit abscission zone (FAZ) was examined in relation to preharvest fruit abscission (PFA) and fruit ripening in ‘Golden Delicious’ and ‘Fuji’ apple (Malus ×domestica Borkh.). PFA, fruit ethylene production, and fruit softening increased rapidly during fruit ripening in ‘Golden Delicious’ apples, whereas no PFA, little fruit ethylene, and gradual fruit softening were recorded in ‘Fuji’ apples. The transcript levels of 1-aminocyclopropane-1-carboxylate (ACC) synthase genes, MdACS1, MdACS3, and MdACS5A, increased rapidly in the fruit cortex of ‘Golden Delicious’ apples during ripening, but not in ‘Fuji’ apples. However, only the level of MdACS5A mRNA was up-regulated in the FAZ of ‘Golden Delicious’ apples. The transcript level of ACC oxidase gene, MdACO1, increased in the fruit cortex for both cultivars but increased only in the FAZ of ‘Golden Delicious’ apples. Expression of the ethylene receptor genes, MdETR1, MdETR2, MdERS1, and MdERS2, increased in the fruit cortex for both cultivars, but only MdETR2 and MdERS2 increased in the FAZ of ‘Golden Delicious’ apples. The transcript levels of MdPG2, a polygalacturonase gene (PG), and MdEG1, a β-1,4-glucanase gene, markedly increased only in the FAZ of ‘Golden Delicious’ apples, whereas only MdPG1 rapidly increased in the fruit cortex of ‘Golden Delicious’ apples. Our results suggested that MdACS5A, MdACO1, MdPG2, and MdEG1 in the FAZ might be related to the difference in PFA between these two cultivars, whereas MdACS1 and MdPG1 were associated with fruit softening.

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Fruit drop in cotton: some causes

Journal of Agriculure and Food ◽

10.52587/jaf040202 ◽

2021 ◽

pp. 36-62

Keyword(s):

Molecular Level ◽

Environmental Stresses ◽

Cell Wall Degrading Enzymes ◽

Fruit Abscission ◽

The Past ◽

Fruit Drop ◽

Hormonal Imbalance ◽

Age Relation ◽

Dim Light ◽

Internal And External Factors

Various aspects of fruit abscission in cotton have been reviewed in the past. Recent advances in this field thus permit consolidation of review of the current research. A major concern among cotton growers is heavy fruit drop, that leads to direct yield loss, which occurs at the expense of squares and young bolls. Shedding of fruiting forms in cotton is the combined consequence of plant itself like hormonal imbalance, plant nutritional status, age relation, and environmental stresses like water deficit, waterlogging, high temperature, dim light, salinity, insects and diseases. These stresses result in prominent signaling modifications like hormonal imbalance. Ethylene is claimed to play a key role in abscission apparently by activating the production of cell wall degrading enzymes such as cellulases and polygalacturonase. The premature dropping of fruiting bodies can significantly increase due to these environmental stresses, which result in severe loss in cotton yield. This article is focused on both internal and external factors that leads to fruit abscission, mechanism of fruit abscission at the physiological, hormonal, and molecular level and trying to point out the missing links on different aspects of plant hormones and environmental stresses regarding fruit abscission. This article also focused on the missing pieces of the very complicated puzzle of fruit abscission process in cotton and elucidation of the mechanism by which plants perceive abscission signals and trigger phytohormone–mediated signal transduction cascades is crucial to devise fruit shedding related breeding and transgenic approaches.

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KNOX protein KNAT1 regulates fruitlet abscission in litchi by repressing ethylene biosynthetic genes

Journal of Experimental Botany ◽

10.1093/jxb/eraa162 ◽

2020 ◽

Vol 71 (14) ◽

pp. 4069-4082

Author(s):

Minglei Zhao ◽

Caiqin Li ◽

Xingshuai Ma ◽

Rui Xia ◽

Jianye Chen ◽

...

Keyword(s):

Ectopic Expression ◽

Ethylene Biosynthesis ◽

Abscission Zone ◽

Biosynthetic Genes ◽

Fruit Abscission ◽

In Vivo Assays ◽

Endogenous Plant Hormones ◽

Fruitlet Abscission

Abstract Abscission is triggered by multiple environmental and developmental cues, including endogenous plant hormones. KNOTTED-LIKE HOMEOBOX (KNOX) transcription factors (TFs) play an important role in controlling abscission in plants. However, the underlying molecular mechanism of KNOX TFs in abscission is largely unknown. Here, we identified LcKNAT1, a KNOTTED-LIKE FROM ARABIDOPSIS THALIANA1 (KNAT1)-like protein from litchi, which regulates abscission by modulating ethylene biosynthesis. LcKNAT1 is expressed in the fruit abscission zone and its expression decreases during fruitlet abscission. Furthermore, the expression of the ethylene biosynthetic genes LcACS1, LcACS7, and LcACO2 increases in the fruit abscission zone, in parallel with the emission of ethylene in fruitlets. In vitro and in vivo assays revealed that LcKNAT1 inhibits the expression of LcACS/ACO genes by directly binding to their promoters. Moreover, ectopic expression of LcKNAT1 represses flower abscission in tomatoes. Transgenic plants expressing LcKNAT1 also showed consistently decreased expression of ACS/ACO genes. Collectively, these results indicate that LcKNAT1 represses abscission via the negative regulation of ethylene biosynthesis.

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586 Cell Wall Protein Differences in Fruits of Two Tabasco Pepper Lines

HortScience ◽

10.21273/hortsci.35.3.497d ◽

2000 ◽

Vol 35 (3) ◽

pp. 497D-497

Author(s):

Ramon A. Arancibia ◽

Carl E. Motsenbocker

Keyword(s):

Cell Wall ◽

Protein Profile ◽

Cell Wall Protein ◽

Abscission Zone ◽

Capsicum Frutescens ◽

Factors Affecting ◽

Fruit Abscission ◽

Detachment Force ◽

Isolation And Characterization

`McIlhenny Select' (easy detachment) and `Hard Pick' are two lines of tabasco pepper (Capsicum frutescens L.) that differ in the fruit detachment characteristics. Cellulase (Cx) and polygalacturonase (PG) activity, extracted from the fruit abscission zone, correlated inversely with the force needed to separate the fruit from the pedicel. A trend of higher Cx and PG is associated with the lower detachment force in the McIlhenny Select line. Differences in the fruit cell wall protein profile between both lines occurred during ripening. Two bands of 23 kDa and 40 kDa were higher in `McIlhenny Select'. A band of approximately 30 kDa was higher in `Hard Pick', while a band of ≈70 kDa increased in both lines. Isolation and characterization of these bands as well as Cx and PG is needed to understand the factors affecting fruit detachment in tabasco pepper.

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