New nucleic acid (I) encoding a protein (P), present in plant cells in both soluble form and bound to starch granules, (a) encodes a 1464 amino acid (aa) of (P) reproduced in the specification； (b) includes the coding region of a 4856 bp sequence reproduced in the specification； (c) can hybridise with (a) or (b)； (d) is degenerate, within the genetic code, with (a)-(c) or (e) is a fragment, deriv. or allelic variant of (a)-(d). Also claimed are: (1) DNA (II) encoding RNA that is antisense to a (I) transcript, has ribozyme activity on this transcript or which when expressed in a plant cell reduces expression of (I) by a co-suppressant effect； (2) nucleic acid fragments (III) of at least 15 nucleotides that hybridise specifically with (I)； (3) plants contg. cells contg. (I) or (II)； and (4) starch obtained from these plants.
