Knob heterochromatin homology in maize and its relatives
We have characterised the major DNA sequence component of knob heterochromatin in maize, teosinte andTripsacum. Sequence analysis of this DNA gives strong support to the proposal that maize originated by selection of variants in teosinte. In situ hybridization has confirmed that this repeating DNA sequence, which is the major component of maize knob heterochromatin, is also the major component of knobs in teosinte,Zea diploperennis andTripsacum. In Southern blot hybridizations the repeat has a similar basic organization in all taxa;Tripsacum, however, is differentiated from maize and teosinte by a number of sequence features. Maize and teosinte knob heterochromatin are indistinguishable with regard to the distribution of mutations in the 180-bp repeat and the presence and organization of a 202-bp variant sequence. The knob DNA sequence was not detectable in three species ofCoix, an Old World genus of the Maydeae.
Within the repeat unit is a 27-bp region that shows no sequence changes in maize, teosinte orTripsacum. The remainder of the repeat unit has randomly distributed nucleotide changes. The presence of the conserved sequence region suggests that knob DNA may have a functional role in the nucleus.
Key wordsHeterochromatin Highly repeated DNA Maize evolution Sequence conservation Knob cytology
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- Beadle GW (1980) The ancestry of corn. Sci Am 242:96–103Google Scholar
- Brown AHD, Clegg MT (1983) Analysis of variation in related DNA sequences. In: Weir BS (ed) Statistical analyses of DNA sequences. Marcel Dekker, New York, pp 107–132Google Scholar
- Galinat WC (1978) The inheritance of some traits essential to maize and teosinte. In: Walden DB (ed) Maize breeding and genetics. John Wiley & Sons, New York, pp 93–111Google Scholar
- Iltis HH, Doebley FJ, Guzman R, Pazy B (1979)Zea diploperennis (Gramineae): a new teosinte from Mexico. Science 203:186–188Google Scholar
- Jain HK (1973) Genetic differentiation of two Himalayan varieties of maize. Ind J Genet Plant Breeding 33:401–415Google Scholar
- Kato Yamakake TA (1975) Cytological studies of maize and teosinte in relation to their origin and evolution. Ph. D. thesis, University of Massachusetts, Amherst and Mass Agric Exp Sta Bull 635 (1976)Google Scholar
- Longley AE (1937) Morphological characters of teosinte chromosomes. J Agric Res 54:835–862Google Scholar
- Longley AE (1941) Chromosome morphology in maize and its relatives. Bot Rev 7:263–289Google Scholar
- Mangelsdorf PC (1974) Corn, its origin, evolution and improvement. Harvard University Press, Cambridge, Massachusetts, pp 1–262Google Scholar
- Mangelsdorf PC, MacNeish RS, Galinat WC (1964) Domestication of corn. Science 143:538–545Google Scholar
- Mangelsdorf PC, Roberts LM, Rogers JS (1981) The probable origin of annual teosinte, Publication 10, The Bussey Institute of Harvard University, Cambridge, MassachusettsGoogle Scholar
- Nirodi N (1955) Studies on Asiatic relatives of maize. Ann Mo Bot Garden 42:103–130Google Scholar
- Pasupuleti CV, Galinat WC (1982)Zea diploperennis: 1. Its chromosomes and comparative cytology. J Hered 73:168–172Google Scholar
- Peacock WJ, Dennis ES, Rhoades MM, Pryor AJ (1981) Repeated DNA limited to knob heterochromatin in maize. Proc Natl Acad Sci USA 78:4490–4494Google Scholar
- Pryor AJ, Faulkner K, Rhoades MM, Peacock WJ (1981) Asynchronous replication of heterochromatin in maize. Proc Natl Acad Sci USA 77:6705–6709Google Scholar
- Rhoades MM (1978) Genetic effects of heterochromatin in maize. In: Walden DB (ed) Maize breeding and genetics. John Wiley & Sons, New York, pp 641–672Google Scholar
- Ward EJ (1980) Banding patterns in maize mitotic chromosomes. Can J Genet Cytol 22:61–67Google Scholar
- Wilkes HG (1967) Teosinte; the closest relative of maize, Bussey Institute, Harvard University, Cambridge, Massachusetts, pp 1–159Google Scholar