Expression of the maize GALACTINOL SYNTHASE gene family:: (II) Kernel abscission, environmental stress and myo-inositol influences accumulation of transcript in developing seeds and callus cells

Accumulation of transcript from three maize (Zea mays L. inbred line B73) GALACTINOL SYNTHASE (ZmGOLS) genes in abscised developing seeds and callus before and after stress was examined. Previous work showed that transcript from ZmGOLS3 predominates during seed development, whereas ZmGOLS2 transcript accumulates when triggered by certain stresses following imbibition. Abscission stimulated accumulation of ZmGOLS transcript in immature kernels. This accumulation was enhanced by increasing durations of dehydration stress. In callus tissue, neither ZmGOLS1 nor ZmGOLS3 was detected regardless of media composition or the nature or duration of the applied stress. Accumulation of ZmGOLS2 transcript in heat- or dehydration-stressed callus was induced by exogenously supplied myo-inositol in low amounts but not by sucrose. However, abundance of transcript was a poor indicator of activity of GOLS or amounts of galactinol/raffinose regardless of type of tissue, composition of media, or imposition of stress. Neither were amounts of galactinol/raffinose tightly associated with activity of GOLS nor amounts of myo-inositol, despite the ability of exogenously supplied raffinose to maintain the growth of dehydration-stressed callus. The abundance of ZmGOLS transcript did not increase in response to exogenously supplied abscisic acid.