Location: Crop Genetics and Breeding ResearchTitle: Exogenous melatonin improves cotton (Gossypium hirsutum L.) pollen fertility under drought by regulating carbohydrate metabolism in male tissues
|HU, WEI - Nanjing Agricultural University|
|CAO, YUTING - Nanjing Agricultural University|
|LOKA, DIMITRA - Aberystwyth University|
|REITER, RUSSEL - University Of Texas At San Antonio|
|ALI, SAIF - Nanjing Agricultural University|
|LIU, YU - Nanjing Agricultural University|
|ZHOU, ZHIGUO - Nanjing Agricultural University|
Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2020
Publication Date: 4/8/2020
Citation: Hu, W., Cao, Y., Loka, D.A., Harris-Shultz, K.R., Reiter, R.J., Ali, S., Liu, Y., Zhou, Z. 2020. Exogenous melatonin improves cotton (Gossypium hirsutum L.) pollen fertility under drought by regulating carbohydrate metabolism in male tissues. Plant Physiology and Biochemistry. 151:579-588. https://doi.org/10.1016/j.plaphy.2020.04.001.
Interpretive Summary: Drought during flower and boll development has negative effects on cotton (Gossypium hirsutum L. ) yields. Exogenous application of melatonin has been previously shown to alleviate the symptoms of abiotic stress including drought in a wide range of plant species by regulating carbohydrate metabolism and energy production. To explore the effects of exogenous melatonin on the carbohydrate balance in drought-stressed floral organs and its relationship with reproductive activities, a greenhouse experiment was conducted to determine the changes in carbohydrate metabolism and reproductive activities that occurred in drought-stressed cotton in response to melatonin added at various concentrations. The addition of melatonin at 100 and 200 µM to drought stressed plants, improved the net photosynthesis rate of the subtending leaves and the assimilate transport to the anthers, pistils, and ovules as compared to the drought stressed plants. Furthermore, the addition of melatonin to drought stressed plants also improved fertilization efficiency and seed set rate under drought stress. High doses of melatonin (1000 µM) caused a lower seed set rate in drought stressed plants. Thus, low doses of melatonin can regulate carbohydrate balance and improve reproduction in drought stressed cotton plants. Further research is needed to see if the positive results of low doses of melatonin application during drought can be replicated in cotton field trials, to identify the ideal time of application, and to assess the economics of application.
Technical Abstract: The objectives of this study were to determine the changes in carbohydrate metabolism and reproductive activities in drought-stressed cotton floral organs in response to melatonin (100, 200 and 1000 µM). Results showed that drought stress (DS) decreased net photosynthetic rate (Pn) and inhibited assimilate transport to anthers, pistils and ovules. However, the application of melatonin (100 and 200 µM) significantly improved Pn and assimilate transport of drought-stressed plants. Melatonin (100 and 200 µM) also increased pollen fertility of drought-stressed anthers due to increased stored starch content caused by enhanced activities of ADP-glucose pyrophosphorylase, soluble starch synthases and granule-bound starch synthase and increased ATP level. For drought-stressed pistils, stored starch before pollination were also increased by 100 and 200 µM melatonin. During pollen tube growth, starch decomposition and sucrose hydrolysis were improved since the application of melatonin (100 and 200 µM) promoted a-amylase activity and aAmy expression and enhanced sucrose synthase, acid and alkaline invertases activities and SusA, INV1 and INV2 expressions in drought-stressed pistils, generating more matter (glucose) and energy (ATP) for pollen tube growth. Finally, melatonin application (100 and 200 µM) improved fertilization efficiency and seed set rate under DS by facilitating entrance of the pollen tubes into the drought-stressed ovules. The highest melatonin concentration (1000 µM) had no effect on fertilization efficiency, but caused lower seed set rate in drought-stressed pistils. These findings suggest that the addition of low doses of melatonin could regulate the carbohydrate balance in drought-stressed floral organs to improve cotton reproductive activities.