Increasing SnRK1 activity with the AMPK activator A-769662 accelerates seed germination in rice.

Sucrose non-fermenting-1-related protein kinase 1 (SnRK1) plays a key role in rice germination. The small molecule drug, A-769662, activates AMP-activated protein kinase, a mammalian homolog of SnRK1. However, it is unknown whether A-769662 activates SnRK1, thereby affecting germination. SnRK1 in desalted extracts from germinating rice seeds was strongly activated by adding A-769662 in vitro. Applying 50 or 100 μM A-769662 accelerated germination and increased the root length, shoot length, and seedling fresh weight. 50 μM A-769662 treatment increased the catalytic activity and phosphorylation of SnRK1 during germination. Transcriptome analysis and biochemical validation were performed to investigate the mechanism whereby A-769662 treatment promoted rice germination. A-769662 treatment promoted starch hydrolysis by increasing the expression and activity of amylase and inhibited starch biosynthesis by decreasing the expression of OsAGPL2 , OsAGPS2a , Wx , and SSIIa. The abscisic acid (ABA) level and gene expression of ABA-induced transcription factors, including OsNF-YC9 , OsNF-YC12 , OsWRKY24 , OsPYL8 , OsMKKK62 , and OsMKKK63 , which reduced the inhibition of germination by ABA were decreased under 50 μM A-769662 treatment. The increased expression of the OsACO3 and OsACO5 genes and increased ethylene levels under A-769662 treatment, which counteracted the inhibition of ABA on germination and, thus, promoted germination. These results demonstrate the activation of A-769662 on SnRK1 and further reveal the regulatory mechanism of A-769662 in rice seed germination and nutrient remobilization. • AMPK activator, A-769662, strongly increases SnRK1 activity in vitro. • A-769662 treatment accelerates germination by affecting amylase gene expression, ABA pathway and ethylene biosynthesis. • SnRK1 may alter T6P level by regulating expression of TPP genes. [ABSTRACT FROM AUTHOR]