Mono- and dinucleotide repeat DNA content differs in dioecious Asparagus (Asparagus officinalis L.)

Asparagus (Asparagus officinalis L.) is a green vegetable with high antioxidant activity among the commonly consumed vegetables. This plant is naturally dioecious and female plants are homozygous for the recessive alleles (mm) while male plants are either homozygous (MM) or heterozygous (Mm) at the sex locus [1]. In the present study we reported that among the expressed gene/gene segments of asparagus deposited into data bases, mononucleotide and dinucleotide repeat contents were significantly different (Table 1) using a computational approach [2]. Results indicated that genes in male asparagus contained more mononucleotides while female contained fewer amounts of mononucleotide repeats containing genes. On the other hand dinucleotide containing genes in female were much higher than that of the male asparagus. Mono- and di-nucleotide repeat content differences between female and male asparagus indicated that microsatellite instability of mono- and di-nucleotide tandem repeat sequences is much higher than tri-, tetra- penta- and hexa-nucleotide repeat sequences. Although repeat content differences among genes have been previously reported in other plant species [3,4] this study is the first report on repeat content differences between plant sexes. Repeat content differences between the sexes may contribute differenzial expression of genes [5] which may affect the chemical properties of asparagus.

Table 1: Repeat content differences between male and female Asparagus officinalis L.

EST: Expressed Sequence Tags, Obs: Observed, Exp: Expected, SSR: Simple Sequence Repeats, ***: statistically significant at P<0.0001.
Sex	# Bases	#EST	# EST-SSR		Mono-		Di-		Tri-		Tetra-		Penta-		Hexa-
			Obs	Exp	Obs	Exp	Obs	Exp	Obs	Exp	Obs	Exp	Obs	Exp	Obs	Exp
Male	4165918	5188	1003	982.5	660	594.4	114	156.0	170	175.6	5.0	3.5	9	10.5	45	42.5
χ2			0.43		22.287***		16.109***		0.38		0.0		0.352		0.388
Female	1812283	3234	407	427.4	193	258.5	110	67.9	82	76.39	0.0	1.5	6	4.6	16	18.5
χ2			0.977		16.635***		26.095***		0.41		1.516		0.464		0.336
Total	5978201	8422	1410		853		224		252		5		15		61

Acknowledgements: This study was supported by the Scientific Research Projects Coordination Unit of Akdeniz University

References: 1. Jamsari, A. et al. (2004) Theor. Appl. Genet. 108:1140–1146.

2. Ince, A.G. et al. (2008) Plant Cell Tissue Organ Cult. 94:281–290.

3. Ince, A.G. et al. (2010) Mol. Breed. 25:645–658.

4. Ince, A.G. et al. (2010) 25:491–499.

5. Ince, A.G., Karaca, M. (2009)J. Sci. Food Agric. 89:168–176.