Quantitative Proteomics Analysis Reveals Proteins Associated with High Melatonin Content in Barley Seeds under NaCl-Induced Salt Stress

Soil salinization
limits hull-less barley cultivation in the Qinghai-Tibet
Plateau of China. However, some wild hull-less barley seeds accumulate
high melatonin (MEL) during germination with improved salt tolerance;
but the mechanism of melatonin-mediated salt tolerance in hull-less
barley is not well understood at the protein level. This study investigated
proteome changes resulting in high melatonin content in germinating
hull-less barley seeds under high saline conditions. The proteome
profiles of seed treatment with 240 mM-NaCl (N), water (H), and control
(C) taken 7 days after germination were compared using the TMT-based
quantitative proteomics. Our results indicate that salt stress-induced
global changes in the proteomes of germinating hull-less barley seeds,
altering the expression and abundance of proteins related to cell
cycle and control, carbohydrate and energy metabolism, and amino acid
transport and metabolism including proteins related to melatonin production.
Furthermore, proteins associated with cellular redox homeostasis,
osmotic stress response, and secondary metabolites derived primarily
from amino acid metabolism, purine degradation, and shikimate pathways
increased significantly in abundance and may contribute to the high
melatonin content in seeds under salt stress. Consequently, triggering
the robust response to oxidative stress occasioned by the NaCl-induced
salt stress, improved seed germination and strong adaptation to salt
stress.