Nitric oxide and light co-regulate glycine betaine homeostasis in sunflower seedling cotyledons by modulating betaine aldehyde dehydrogenase transcript levels and activity

Abstract

Glycine betaine (GB), an osmolyte, is produced in chloroplasts by the action of betaine aldehyde dehydrogenase (BADH) on its precursor betaine aldehyde. The present work highlights the significance of nitric oxide (NO) in GB homeostasis as a long-distance salt (120 mM NaCl) stress-elicited response. In light-grown seedling cotyledons, both the activity and transcript levels of BADH are much higher than in dark-grown seedlings irrespective of salt stress. Significantly high accumulation of GB in dark-grown seedling cotyledons indicates its preferential mobilization from cotyledons to other plant parts in light-grown seedlings. NO donor application (diethylenetriamine) maintains high BADH activity in light, although in dark it is brought down marginally. BADH levels are maintained high in light than in dark in respective treatments. Reversal of the effect of NO donor on agedependent GB content, BADH activity, and transcript levels by NO scavenger (diethyldithiocarbamate) further demonstrates the impact of NO on GB homeostasis in light-and dark-grown seedlings in an age-dependent manner, major modulation being observed in 4-d-old seedlings. The present work, thus, provides new information on co-regulation of GB homeostasis by NO and light. It also puts forward new information of GB-NO crosstalk in maneuvering salt stress sensing as a longdistance response in seedlings.

Nitric oxide mediated mechanisms adopted by plants to cope with salinity

“…Application of diethylenetriamine, a NO donor also contributed in maintaining the activity of BADH, hence maintaining the homeostasis of GB. It suggests a possible crosstalk between NO and GB in counterattacking the salinity stress (Kumari et al 2019). This modification in the GB content occurs after application of NO due to BADH transcriptional regulation or nitrosylation.…”

“…Glycine-betaine (GB) plays crucial role in regulation of salt stress in plants. Nitric oxide also helps in regulating the GB mediated stress responses in salt stressed plants (Kumari et al 2019). Further, these researchers observed that transcription and activity of betaine aldehydedehydrogenase (BADH) in light-grown seedling cotyledons were found to be very high in comparison to those seedlings which were grown in dark when facing the salinity stress.…”

The light and dark sides of nitric oxide: multifaceted roles of nitric oxide in plant responses to light

“…Light and NO can also co-regulate plant responses to other abiotic stresses (Lee et al, 2008;Liu and Guo, 2013;Kumari et al, 2019). In sunflower seedling cotyledons, the biosynthesis of the osmolyte glycine betaine (GB) was differentially modulated by NO under light and dark conditions, with light restricting its NO-induced accumulation (Kumari et al, 2019). In gsnor1 missense and null Arabidopsis mutants, unusual thermotolerance has been observed depending on the light conditions (Lee et al, 2008).…”

Biochemical mechanisms regulating salt tolerance in sunflower

“…Differential spatial distribution and modulation of SOD isoforms -Cu-ZnSOD and MnSOD is observed in response to melatonin. 18,53,54 Nitric oxide regulates glycine betaine and polyamines homeostasis Sunflower seedling cotyledons have been observed to constitutively accumulate some amount of GB, an osmolyte 55 Sensing of salt stress enhances tissue GB levels by several folds. NO appears to be a key regulator of GB accumulation in seedling cotyledons through modulation of the activity and abundance of betaine aldehyde dehydrogenase (BADH), the key biosynthetic enzyme for GB.…”

“…Work on NO acting as a key molecule in GB and polyamine homoestasis needs to be taken up for further investigations. GB has been recently shown to interact with NO 55 GB-NO could be one of the key molecular interactions regulating plant growth under salt stress. NO and melatonin together seem to serve as key molecules through which plant cells are likely to facilitate salt tolerance at molecular level through their multifarious biochemical interactions.…”