Institute of Genetics, Academy of Sciences of Moldova

Testing the marker line wx sh carrying a mutation phenotypically resembling Dt (9S) for the presence in its genome of regulatory elements Uq and Mrh following pollen treatment with exogenous DNA
--M.K Haritonova, N.V. Krivov and V.N. Lysikov

The occurrence in the aleurone layer of colored dots is most likely to be due to the interaction between the dominant Dt-like element and a receptor allele presumably located in a1. The number and size of the colored sectors in the aleurone layer in different kernels of the same ear indicate that mutation events occur with different frequencies and differ from one another chronologically (McClintock, 1951; Peterson, 1966).

In order to ascertain whether one of the already known regulatory elements has been integrated into the recipient line, plants grown from colorless kernels and yielding upon selfing only colorless progeny, and the parental marker line wx sh, were testcrossed with the tester lines a-dt (Dt), a-ruq (Uq), and a-mrh (Mrh) kindly supplied by Prof. P.A. Peterson. The crosses were made according to the following scheme:

1. M1 with colorless aleurone x tester carrying the receptor. F1 seeds with colorless aleurone, with dotted and with self-colored aleurone.

2. Parental marker line, wx sh, x tester carrying the receptor. F1 seeds with colorless aleurone, with dotted and with self-colored aleurone.

The progeny of the crosses were tested according to the procedure used by Peterson and Salamini (1986).

The M2 ears showed segregation for ear color, so it was possible to select families in which all the kernels had colorless aleurone. It was assumed that these families lacked one of the active elements of the system (either receptor or regulator). Crossing the plants grown from these seeds with tester lines carrying one of the receptors will make it possible to identify maize plants which have acquired active regulatory elements. Accordingly, the presence of a regulatory element will provide an indirect proof of one of the mutator systems being involved in the expression of the Dt-like pattern, and the basis for discussing the possibility of this regulatory element being integrated into the genome as a result of pollen treatment with exogenous DNA.

Testcrosses revealed the presence in all lines carrying the Cg2 and Cg2+ alleles of some regulatory elements of all the five mutator systems examined (Table 1). Therefore, the exogeneous DNA isolated from zb*-8 lg g12 v4 Ch/+++++ Cg2 seedlings might have carried all five regulatory elements. The recipient (the marker line wx sh) only has En/+ in some plants. Families carrying alleles for the Dt-like pattern exhibited activation of the Mrh and Uq regulatory elements (Table 2). At present, a testcross is underway to detect active genetic elements Dt, Ac, En and others.

Table 1. The results of testing lines carrying Cg2 and Cg2+ alleles, as well as MKO1 and wx sh lines for presence of the regulatory elements Dt, Ac, En, Uq and Mrh.

Number of ears carrying regulatory elements

Tested lines DtDt Dt+ ++ AcAc Ac+ ++ EnEn En+ ++ UqUq Uq+ ++ MrhM rh Mrh+ ++
Cg2 gs bm2 gl 2 5 4 2
C g 2 +/Cg2+* 1 3 2 1 4 3
C g 2 +/ Cg2+** 2 4 1 4
Cg2m-s 2 2 7 6
br*-220 4 5 8 9 1 7
sr*-220 6 5 8 6 9
ys*-253 9 6 9 9 9
ys*-143 1 1 1 9 1 4 5 6
MKO1 4 4 5
wx sh 2 6 1 7 9 6
*(Cg2+-- Cg2) j
**(Cg2+-- Cg2) 5369

Table 2. The results of analysis of ears obtained in crosses of the wx sh dt-*7 mutant with tester lines.
Aleurone color
Cross Combinations colorless dotted self-colored
wx sh dt-*7 x a-ruq 13 -- 5
13 6 --
36 102 1
68 57 --
wx sh dt-*7 x a-mrh 48 1 --
5 2 --
7 -- --
16 9 --
6 2 --

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