Toxicity of cyanidin and anthocyanidin 3-glucoside accumulation in the gametophyte
--Taylor, R; Chiusi, A and Walbot, V

Functional maize pollen is yellow due to the presence of flavonoids which are required for germination of the pollen. Production of anthocyanin in the pollen can be obtained via expression of the r-ch:Hopi gene, an allele of R. R is a regulator of anthocyanin biosynthesis. A proportion of plants carrying this allele in combination with Pl produces varying degrees of expression from yellow to dark red pollen. It is presently unknown whether this anthocyanin accumulation is due to sporophytic or gametophyte gene expression. To test whether anthocyanin intermediates, cyanidin and cyanidin 3-glucoside accumulated by bz1 and bz2, had an effect on pollen viability, we compared segregation ratios of pollen with and without anthocyanin. These anthocyanin intermediates are known to be toxic to maize plants when expressed at high levels. We used plants with genotypes Bz1/bz1 and Bz2/bz2 which also contained at least one copy of r-ch:Hopi and Pl. Reciprocal crosses were made to bz1 and bz2 tester and ears were analyzed for their segregation ratio. If the accumulation of these products had no effect on the viability of the pollen we would expect purple to bronze kernels at a ratio of 1:1. The table shows the segregation ratios for the test crosses.

No significant differences in the segregation ratios were observed between the yellow pollen and red pollen crosses. The segregation ratios were 1:1 among test and control crosses. Therefore pollen viability does not seem to be affected by the accumulation of cyanidin and/or cyanidin 3-glucoside. To ascertain whether there is a sporophytic effect, the toxic affects of homozygous bz1 and bz2 r-ch:Hopi plants are now being examined .
 
 
Bronze1
 
Bronze2
 
Number of ears (95%)
 
Number of cases (95%)
 
Segregation ratios (purple:bronze)
 
Segregation ratios (purple:bronze)
Color
1:1
>1:1
1:>1
Color
1:1
>1:1
1:>1
Yellow
8
0
0
Yellow
21
1
0
Red
9
1
0
Red
13
1
0
Pink
3
0
0
Pink
5
1
0


Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors

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