Inhibition of SAH-hydrolase activity during seed germination leads to deregulation of flowering genes and altered flower morphology in tobacco

Abstract

Developmental processes are closely connected to certain states of epigenetic information which, among others, rely on methylation of chromatin. S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) are key cofactors of enzymes catalyzing DNA and histone methylation. To study the consequences of altered SAH/SAM levels on plant development we applied 9-(S)-(2,3-dihydroxypropyl)-adenine (DHPA), an inhibitor of SAH-hydrolase, on tobacco seeds during a short phase of germination period (6 days). The transient drug treatment induced: (1) dosage-dependent global DNA hypomethylation mitotically transmitted to adult plants; (2) pleiotropic developmental defects including decreased apical dominance, altered leaf and flower symmetry, flower whorl malformations and reduced fertility; (3) dramatic upregulation of floral organ identity genes NTDEF, NTGLO and NAG1 in leaves. We conclude that temporal SAH-hydrolase inhibition deregulated floral genes expression probably via chromatin methylation changes. The data further show that plants might be particularly sensitive to accurate setting of SAH/SAM levels during critical developmental periods.

Functional Characterization of SlSAHH2 in Tomato Fruit Ripening

“…Also, only mutations in AtSAHH1 were embryonic lethal though sequences between the two AtSAHH genes shared higher than 80% identity (Furner et al, 1998; Rocha et al, 2005). Transgenic tobacco expressing antisense RNA of NtSAHH was stunted, dwarf, absent of apical dominance and seized of floral abnormalities (Tanaka et al, 1997; Fulneček et al, 2011). Co-silencing of SlSAHH genes by VIGS (virus induced gene silencing) in tomato increased immunity to Pst DC3000 and enhanced tolerance to drought stress (Li et al, 2015).…”

Hypomethylating drugs efficiently decrease cytosine methylation in telomeric DNA and activate telomerase without affecting telomere lengths in tobacco cells

“…DHPA was originally found to have a broad-spectrum antiviral activity (De Clercq et al 1978) and its hypomethylating impact was discovered only later (Š ebestová et al 1984). At present, a number of experimental studies using this drug are available, including its use in plant systems (Fojtova et al 1998;Kovarik et al 2000;Fulnecek et al 2011).…”

How to interpret Methylation Sensitive Amplified Polymorphism (MSAP) profiles?

“…Fragments 1 and 3 represent the (-, +) MH pattern, fragment 2 represents the (+, +) MH pattern, and fragment 4 represents the (+, -) MH pattern. Note that fragments 1 and 3 disappear after application of the combination of the Hpa II, Msp I and EcoR I enzymes (M + H panel) or after DNA hypomethylation (H_h panel) by 100 μM DHPA [48]. Each restriction fragment is represented by two peaks (green and blue) derived from two complementary DNA strands (differently labeled selective primers were used).…”

“…We used DNA samples isolated from tobacco seedlings treated with 0, 10, and 100 μM 9-( S )-(2,3-dihydroxypropyl)-adenine (DHPA) and analyzed previously by Msp I/ Hpa II digestion and Southern blot hybridization [48]. DHPA is a reversible competitive inhibitor of S -adenosylhomocysteine-hydrolase that elevates the intracellular SAH concentration [49].…”

“…SAH competes with S -adenosylmethionine (SAM), leading to inhibition of most SAM-dependent methyltransferases. In plants, DHPA treatment induces hypomethylation of CHG sites preferentially (CHG DNA methylation represents a metabolic bottleneck due to its dependence on histone methylation) and also hypomethylation of CG sites to some extent at elevated DHPA concentrations [48]. …”