Figure 4.

(a) Phenotypic variation of the plants after five generations of selfing. The plants include two parents, A. thaliana autotetraploid (At4) and A. arenosa (Aa), six allotetraploids (S–1 to S–6), and a natural allotetraploid, A. suecica (As). Allotetraploids have the same chromosome number (Figure 3c and data not shown) but display phenotypic and flowering-time variation. Some plants (S5–5 and S5–6) resemble A. suecica, whereas others (S5–1 to S5–4) show novel phenotypes. Differential expression of parental genes may contribute to the phenotypic variation of Arabidopsis allotetraploids. (b) Evidence for epigenetic silencing in resynthesized allopolyploids. A. suecica (As, white flower) is the naturally occurring allotetraploid derived from A. thaliana (not shown) and A. arenosa (Aa), which have white and pink flowers, respectively. The flower colors in the third generation of resynthesized allotetraploids (S3–1, 2, and 3) segregate from all white (S3–1) to all pink (S3–3). Variegated flower colors in the same inflorescence branch (S3–2) indicate epigenetic regulation of genes controlling flower color pathways. The same-size bars are 50 mm in (a), except for At4, and 5 mm in (b), except for As.