Effects of Exogenous Regulation of Ethylene and Abscisic Acid on Grain-Filling and Endosperm PCD of Wheat Under Drought Stress After Anthesis

Although studies have shown that grain-filling and programmed cell death of wheat endosperm are affected by drought stress, which is closely related to ethylene and abscisic acid.The mechanism of ethylene and abscisic acid regulate grain-filling and endosperm PCD under drought stress is remains unclear. In this study, we regulated the production of ethylene and abscisic acid in wheat grains under drought stress at filling stage by chemicals. The results showed that spraying ethylene synthesis inhibitor enhanced endosperm cell viability, delayed nuclear deformation, and decreased ACC content. Compared with the CK, the CN significantly decreased the DNA hydrolase activity and significantly increased the DNA content. In addition, the CN treatment reduced the expression of four genes related to ethylene receptors (ers1, ers2 etr1, etr2) and increase the expression of dad1. Under CN treatment, the process of endosperm PCD was delayed, the duration of high grouting rate was prolonged, and the grain weight was increased, in contrast, the opposite result was obtained after spraying abscisic acid synthesis inhibitor. The production of abscisic acid and ethylene in grains determines the fate of endosperm cells. A new model of artificial regulation of abscisic acid and ethylene, delaying endosperm PCD process and increasing grain weight under post-anthesis drought was proposed.

Ethylene-regulated immature fruit abscission is associated with higher expression of CoACO genes in Camellia oleifera

Immature fruit abscission is a key limiting factor in Camellia oleifera Abel. ( C. oleifera ) yield. Ethylene is considered to be an important phytohormone in regulating fruit abscission. However, the molecular mechanism of ethylene in regulating fruit abscission in C. oleifera has not yet been studied. Here, we found that the 1-aminocyclopropane-1-carboxylic acid (ACC) content was significantly increased in the abscission zones (AZs) of abnormal fruits (AF) which were about to abscise when compared with normal fruits (NF) in C. oleifera ‘Huashuo’. Furthermore, exogenous ethephon treatment stimulated fruit abscission. The cumulative rates of fruit abscission in ethephon-treated fruits (ETH-F) on the 4th (35.0%), 8th (48.7%) and 16th (57.7%) days after treatment (DAT) were significantly higher than the control. The ACC content and 1-aminocyclopropane-1-carboxylate oxidase (ACO) activity in AZs of ETH-F were also significantly increased when compared with NF on the 4th and 8th DAT. CoACO1 and CoACO2 were isolated in C. oleifera for the first time. The expressions of CoACO1 and CoACO2 were considerably upregulated in AZs of AF and ETH-F. This study suggested that ethylene played an important role in immature fruit abscission of C. oleifera and the two CoACOs were the critical genes involved in ethylene's regulatory role.

Melatonin enhances salt tolerance by promoting MYB108A-mediated ethylene biosynthesis in grapevines

The signal molecules melatonin and ethylene play key roles in abiotic stress tolerance. The interplay between melatonin and ethylene in regulating salt tolerance and the underlying molecular mechanism of this interplay remain unclear. Here, we found that both melatonin and 1-aminocyclopropane-1-carboxylic acid (ACC, a precursor of ethylene) enhanced the tolerance of grapevine to NaCl; additionally, ethylene participated in melatonin-induced salt tolerance. Further experiments indicated that exogenous treatment and endogenous induction of melatonin increased the ACC content and ethylene production in grapevine and tobacco plants, respectively. The expression of MYB108A and ACS1, which function as a transcription factor and a key gene involved in ethylene production, respectively, was strongly induced by melatonin treatment. Additionally, MYB108A directly bound to the promoter of ACS1 and activated its transcription. MYB108A expression promoted ACC synthesis and ethylene production by activating ACS1 expression in response to melatonin treatment. The suppression of MYB108A expression partially limited the effect of melatonin on the induction of ethylene production and reduced melatonin-induced salt tolerance. Collectively, melatonin promotes ethylene biosynthesis and salt tolerance through the regulation of ACS1 by MYB108A.

Ethylene-dependent effects on generative organ abscission of Lupinus luteus

The abscission of certain organs from the plant is part of the fulfilment of its developmental programs. The separation process occurs in a specialized abscission zone usually formed at the base of detached organ. The changing level of phytohormones, particularly ethylene, is the element responsible for coordinating anatomical and physiological transformation that accompanies organ abscission. The application of ethylene (ET) on <em>Lupinus luteus</em> stimulates flower abortion. However, the treatment with 1-aminocyclopropane-1-carboxylic acid (ACC) – direct ET precursor – does not cause such a strong physiological response. In turn, when applied on the pedicels both ET biosynthesis (2-aminoethoxyvinylglycine; AVG) and action (norbornadiene; NBD) inhibitors reversed the stimulatory effect of ET on generative organ separation. In order to determine ET role in the flower abscission process in <em>L. luteus</em>, we identified the sequences coding for synthase (<em>LlACS</em>) and oxidase (<em>LlACO</em>) of ACC and measured their expression levels. Abscission zone activation is accompanied by a considerable increase both in <em>LlACS</em> and <em>LlACO</em> cDNAs and also ACC content, which is specifically localized in the dividing cells at the base of the flower being detached. Obtained results suggest that ET is a strong stimulator of flower abortion in <em>L. luteus</em>.

ROLE OF POLYAMINES IN INHIBITION OF ETHYLENE BIOSYNTHESIS AND THEIR EFFECTS ON RICE ANTHER CULTURE DEVELOPMENT

The polyamines such as putrescine, spermidine, and spermine were reported to increase green plant regeneration in rice anther culture. Low response of anther culture of rice sub-species indica may be improved with the addition of putrescine in the culture media. Four experiments were conducted to study the role of polyamines in inhibition of ethylene biosynthesis and their effects on rice anther culture development. Anthers of two subspecies of rice, indica (IR64, Krowal, Jatiluhur) and japonica (Taipei 309) were cultured onto media supplemented with putrescine (N6P) and without putrescine (N6). Young<br />panicles containing the anthers at mid-to-late nucleate microspores were cold pretreated at 5 + 2°C and incubated in the dark for 8 days before the anthers were cultured. Results<br />showed that medium without putrescine produced an earlier senescence of indica rice anther than that of japonica. The addition of 10-3 M putrescine into the culture media inhibited ethylene biosynthesis as anther senescence delayed, increased the three polyamines contents, and decreased the ACC content as well as ACC oxydase activity in anther-derived calli. In the anther and anther-derived calli of subspecies indica, the total<br />polyamines content was lower (10.14 nM g-1 anther and 8.48 nM g-1 calli) than that of subspecies japonica (12.61 nM g-1 anther and 10.16 nM g-1 calli), whereas the ethylene production was higher (32.31 nM g-1 anther and 2.48 nM g-1 calli) than the japonica (31.68 nM g-1 anther and 1.76 nM g-1 calli). This study suggests that application of 10-3 M putrescine in anther culture of rice subspecies indica improves androgenesis by inhibiting<br />early senescence of cultured anthers and enhancing embryo or callus formation from microspores.

ROLE OF POLYAMINES IN INHIBITION OF ETHYLENE BIOSYNTHESIS AND THEIR EFFECTS ON RICE ANTHER CULTURE DEVELOPMENT

The polyamines such as putrescine, spermidine, and spermine were reported to increase green plant regeneration in rice anther culture. Low response of anther culture of rice sub-species indica may be improved with the addition of putrescine in the culture media. Four experiments were conducted to study the role of polyamines in inhibition of ethylene biosynthesis and their effects on rice anther culture development. Anthers of two subspecies of rice, indica (IR64, Krowal, Jatiluhur) and japonica (Taipei 309) were cultured onto media supplemented with putrescine (N6P) and without putrescine (N6). Young<br />panicles containing the anthers at mid-to-late nucleate microspores were cold pretreated at 5 + 2°C and incubated in the dark for 8 days before the anthers were cultured. Results<br />showed that medium without putrescine produced an earlier senescence of indica rice anther than that of japonica. The addition of 10-3 M putrescine into the culture media inhibited ethylene biosynthesis as anther senescence delayed, increased the three polyamines contents, and decreased the ACC content as well as ACC oxydase activity in anther-derived calli. In the anther and anther-derived calli of subspecies indica, the total<br />polyamines content was lower (10.14 nM g-1 anther and 8.48 nM g-1 calli) than that of subspecies japonica (12.61 nM g-1 anther and 10.16 nM g-1 calli), whereas the ethylene production was higher (32.31 nM g-1 anther and 2.48 nM g-1 calli) than the japonica (31.68 nM g-1 anther and 1.76 nM g-1 calli). This study suggests that application of 10-3 M putrescine in anther culture of rice subspecies indica improves androgenesis by inhibiting<br />early senescence of cultured anthers and enhancing embryo or callus formation from microspores.

Effects of 1-MCP Treatment on the Ethylene Synthesis of Postharvest Yali Pear Seeds

The effects of 1-MCP treatment on the ethylene synthesis of Yali pear seeds of different harvest maturity were evaluated during storage. Yali pear fruit (early harvested and late harvested) were treated with 1.0 μL.L-11-MCP for 20 h at room temperature, packaged in PE plastic film and then stored at 0±1°C for 180 days. The results show that the respiration, ethylene production, ACC content, ACO and ACS activities of the seeds of early harvested Yali pear fruit with 1-MCP treatment decrease significantly during storage, the peaks decrease and are delayed for 60 days. But 1-MCP treatment has no significant effects on the indexes related with ethylene synthesis to the seeds of late harvested fruit. 1-MCP can be used to inhibit the synthesis of ethylene in the seeds effectively and keep the quality and extend the shelf life of early harvested Yali pear fruit.

Effects of Anti-Ethylene Treatments on Ethylene Production and Antioxidant Activities in Cut Spray Carnation

The present investigation was aimed to study changes in ethylene production, ACC content and antioxidant enzymes of cut spray carnation (Dianthus caryophyllus L.) flowers that had been treated with amino-oxyacetic acid (AOA), benzyladenine (BA) and 1-methylcyclopropene (1-MCP). Maximum vase life in ‘Optima’ spray carnations was obtained with 0.6 mg l-1 1-MCP. Ethylene production was significantly decreased by AOA at concentrations over 100 mg l-1, BA at 30 mg l-1, and 1-MCP at all concentrations, compared with the control. A significant increase in ACC content was observed in 1-MCP treated cut flowers compared with the control. However, the decline in ACC content was observed after using 100 or 150 mg l-1 AOA. A significant increase in SOD, CAT and POX enzyme activities was observed in the treatment with 0.6 mg l-1 1-MCP.