Polyamines in the life of Arabidopsis: profiling the expression of S-adenosylmethionine decarboxylase (SAMDC) gene family during its life cycle

Table 3 Number of synonymous to non-synonymous substitutions among coding sequences of the SAMDC genes estimated using K-estimator software by Yang and Nielson method [45]

Sequence compared	Ka	Ks	Ka/Ks	P-Value	Type of selection	S	N	Divergence-Time
AtSAMDC1vs2	2.24	2.50	0.89	0.73	Purifying	156	468	2.30
AtSAMDC1vs3	2.03	3.94	0.52	0.0001**	Purifying	159	420	2.49
AtSAMDC1vs4	4.75	2.06	2.31	0.01**	Positive	158	432	3.95
AtSAMDC2vs4	2.89	4.11	0.70	0.72	Purifying	154	452	3.19
AtSAMDC3vs5	3.19	1.59	2.01	0.03*	Positive	130	420	2.78

Ka - rate of non-synonymous substitutions; Ks - rate of synonymous substitutions; Ka/Ks - ratio of non-synonymous to synonymous substitutions; S - number of synonymous substitutions; N - number of non-synonymous substitutions. Divergence time per site per year is estimated by Ka/Ks – Calculator, which is a weighted average of synonymous substitution rate and non-synonymous substitution rate. Significance is tested by Fisher exact test; * denotes P < 0.05, ** denotes P < 0.01. A significant value for positive selection indicates higher rate of non-synonymous substitutions and purifying indicates higher rate of synonymous substitutions

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