Isolation of early genes expressed in reproductive organs of the dioecious white campion (Silene latifolia) by subtraction cloning using an asexual mutant

Abstract

SummaryThe dioecious white campion (Silene latifolia) has been chosen as a working model for sexual development. In this species, sexual dimorphism is achieved through two distinct developmental blocks: inhibition of carpel development in male flowers, and early arrest of anther differentiation in female flowers. The combined advantages of the dioecious system and the availability of a sexual mutant lacking both male and female reproductive organs have been exploited in a molecular subtraction approach using male and asexual flower buds. This resulted in the cloning of 22 cDNA clones expressed in stamens at distinct stages of development. Fourteen of these clones corresponded to genes whose expression was detected in pre-meiotic stamens, a stage of development for which very little information is presently available. Furthermore, the absence of similarities with database sequences for ten clones suggests that they represent novel genes. Functional analysis of each clone will enable their positioning within the reproductive organ developmental pathway(s). In parallel, these clones are being exploited as developmental markers of early differentiation within the flower.

Stamen Structure and Function

“…Stamen expression studies have been conducted in many crop and model species, including tomato (Ursin et al, 1989;Chmelnitsky et al, 2003), tobacco (Koltunow et al, 1990), Antirrhinum (Nacken et al, 1991), oilseed rape (Scott et al, 1991b;Shen and Hsu, 1992), maize (Wright et al, 1993), rice (Tsuchiya et al, 1994), lily (Crossley et al, 1995), white campion (Barbacar et al, 1997), Lotus japonicus (Endo et al, 2002), and Arabidopsis (Rubinelli et al, 1998;Sablowski and Meyerowitz, 1998;Amagai et al, 2003;Zik and Irish, 2003). Some of these studies have manipulated B and/or C class genes themselves to help identify their targets; these experiments are discussed in more detail below.…”

Plant sex determination and sex chromosomes

“…Isolation of male-specific cDNAs from developing flower buds or reproductive organs has not yet led to discovery of sex determining genes (Matsunaga et al, 1996;Barbacar et al, 1997), probably because sex-determi-nation happens very early in flower development , so the genes identified are controlled in response to sex, rather than the controlling loci. Genes known to be important in floral development, including the homoeotic MADS-box genes also appear not to have direct roles in sex determination (Hardenack et al, 1994;Ainsworth et al, 1995).…”

Male-fertility genes expressed in male flower buds of Silene latifolia include homologs of anther-specific genes

“…Seventy two clones showed no homology with the any protein within the GenBank, 18 clones were ribosomal protein, 11 clone showed similarity with expressed protein with no specific function, and 151 clone showed homology with known genes in organisms other than S. latifolia . Thirty-six clones of the sequenced 288 clones corresponded to previously identified male-specific S. latifolia genes, including men2 , men3 , men8 , men9 , men369 (Scutt et al, 1997;Scutt et al, 2002), MROS3A , MROS3B (Matsunaga et al, 1996), ST1 (Lebel-Hardenack et al, 1997), CCLS4 (Barbacar et al, 1997), SlX1 (Delichere et al, 1999), and SLP2 (Pritham et al, 2003).…”