Gene symbol for the erectoides-type, short-internode mutant Wt 11242

Murfet, I.C.                                                School of Plant Sci., Univ. of Tasmania, Hobart, Australia

      The gene responsible for the short-internode phenotype of mutant line Wt11242 has now been assigned two different symbols. Recently, Święcicki and Wolko (8) designated the mutant allele dnd (densinodosum) and showed Dnd was located in the M region of linkage group III. Earlier, Kusnadi et al. (2) found the Wt11242 mutant had an erectoides-type phenotype and was allelic with the semi-erectoides mutant lka characterized by Reid and Ross (5). They designated the second mutant allele lka¹¹²⁴². However, in the terminology now adopted by the Hobart pea group, the two mutant alleles would be written as lka1-1 (type line WL5865) and lka1-2 (type line Wt11242).

      There are five loci in the erectoides series: Lk, Lka, Lkb, Lkc and Lkd (1, 4-6). The erectoides phenotype is characterized by short internodes, stiff stems, short peduncles and petioles, dark green leaves, some epinasty, and an absence of basal branching. In the lka mutants, the shorter internodes result from a reduction in both cell length and cell number (2, 5). The erectoides phenotype appears to result from impaired brassinosteroid synthesis or reception. Mutants lk and lkb are brassinosteroid deficient: the lkb mutation blocks conversion of 24-methylenecholesterol to campesterol (3) and lk blocks conversion of campesterol to campestanol (9). The lka1-1 mutant is brassinosteroid insensitive (3). Response of mutant lka1-2 has not been reported. The lka1-2 mutation appears less severe than lka1-1 (2). The plant brassinosteroid growth regulators are related to animal steroidal hormones. The pea Lkb gene has been sequenced and the amino acid sequence showed 60% similarity with the human homologue (7).

1.      Cramp, R.E. and Reid, J.B.  1993.  Plant Growth Regul. 12: 141-147.

2.      Kusnadi, J., Gregory, M., Murfet, I.C., Ross, J.J. and Bourne, F.  1992.  Pisum Genetics 24: 64-74.

3.      Nomura, T., Kitasaka, Y., Takasuto, S., Reid, J.B., Kukami, M. and Yokota, T.  1999.  Plant Physiol. 119: 1517-1526.

4.      Reid, J.B.  1986.  Ann. Bot. 57: 577-592.

5.      Reid, J.B. and Ross, J.J.  1989.  Physiol. Plant. 75: 81-88.

6.      Reid, J.B., Ross, J.J. and Hasan, O.  1991.  J. Plant Growth Regul. 10: 11-16.

7.      Schultz, L., Kerckhoffs, H.J., Klahre, U., Yokota, T. and Reid, J.B.  2001 . Plant Mol. Biol. (in press).

8.      Święcicki, W.K. and Wolko, B.  2000.  Pisum Genetics 32: 48-50.

9.   Yokota, T., Nomura, T., Kitasaka, Y., Takasuto, S. and Reid, J.B.  1997.  Proc. Plant Growth Regul. Soc. USA 24: 99.