Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 5.25

DEVELOPING CHICKPEA SEEDS ASSIMILATE SULPHUR, AND INCREASE THEIR ACCUMULATION OF SULPHUR AMINO ACIDS IN RESPONSE TO INCREASED DEMAND FROM AN ADDED TRANSGENE ENCODING A SULPHUR RICH PROTEIN

P. CHIAIESE*, L. MOLVIG*, C. HOCART**, T.J.V. HIGGINS*, L.M. TABE*

*) CSIRO Plant Industry, GPO Box 1600 Canberra ACT 2601, Australia

**) Research School of Biological Science, GPO Box 475, Canberra, ACt 2601, Australia

chickpea, sulphur amino acids, sunflower seed albumin

Increase evidence supports the hypothesis that reproductive sink organs are active in sulphur assimilation. In this stud, developing embryos of chickpea (Cicer arietinum L) were demonstrated to contain significant reserves of sulphur in an oxidised form. The concentration of oxidised sulphur decreased while the concentration of reduced sulphur and nitrogen increased during embryo maturation, consistent with the premise that oxidised sulphur is reduced and assimilated in the developing embryo. It was shown that developing chickpea cotyledons could incorporate the sulphur atom from sulphate into protein, and that embryos contained significant amounts of two enzymes of the cysteine biosynthetic pathway. Transgenic chickpea containing a seed-expressed gene for a sulphur-rich sunflower albumin, contained more seed methionine and less oxidised sulphur than controls, suggesting that introduction of an additional sulphur demand stimulated sulphur reduction in the transgenic seeds. Seeds of two transgenic lines that accumulated large amounts of the sunflower albumin had undetectable levels of oxidised sulphur, altered total seed protein profile, and diminished activities of proteinase inhibitors, compared to non-transgenic seeds of the parental chickpea cultivar. It appeared that reduced sulphur sequestered into sunflower albumin was supplied by additional sulphur assimilation in the developing embryo, as well as some diversion of sulphur amino acids from endogenous seed protein.