Lipid biosynthesis in seeds of mustard (Brassica juncea) influenced by zinc and sulphur deficiency

Abstract

In developing seeds of mustard (Brassica juncea L. cv. RLM 198) the period between 20 and 30 days after fertilization (DAF) was identified as the period of active lipid biosynthesis, although dry matter continued to accumulate until maturity. The period of lipid synthesis was associated with a decrease in starch, soluble sugars and protein, thus, giving rise to precursors for the biosynthesis of lipids. Besides decreasing the dry matter content (on both % and seed basis), Zn and S deficiency caused a significant (P > 0.05) reduction in oil content. As compared to control, the decrease in oil content was 11, 12 and 18% at 30 DAF and 4, 9 and 16% at maturity in Zn, S and (Zn+S) deficient treatments, respectively. Throughout the period of seed development, a significant decrease in starch and protein with a slight accumulation of soluble sugars was observed due to deficiency of Zn or S. The rate of [l‐14C]‐acetate incorporation into total lipids, which was maximal at 30 DAF, also displayed a significant decrease due to the abovementioned mineral deficiencies. Addition of Zn or S in vitro, enhanced the lipid synthesis at all stages of seed development. Under Zn and S deficiency, the phospholipids increased from 10 to 30 DAF and then declined until maturity. However, the proportion of glycolipids and free fatty acids increased, with a corresponding decrease in total glycerides. Further, in deficiency treatments, there was an increase in 22:1 with a corresponding decrease in 18:1, 18:2 and 18:3 in developing and mature mustard seeds.

Oil biosynthesis and its related variables in developing seeds of mustard (Brassica juncea L.) as influenced by sulphur fertilization

“…Irrespective of the treatments, total sugar content started decreasing from 10 DAF until harvest (HR). These findings agree with some earlier studies in oilseed crops (Ahmad et al 2000;Fazli et al 2005a;Munshi et al 1990). Application of S (T2) increased the total sugar content at all the stages of seed development compared to -S treatment (T1).…”

“…Irrespective of the treatments, oil accumulation in the seeds commenced at 10 DAF and continued till 30 DAF, beyond which no significant increase was observed. These findings are in agreement with some earlier studies in oilseeds (Abdin et al 2003; Ahmad and Abdin 2000a; Ahmad et al 2000;Chung et al 1995;Fazli et al 2005a,b;Munshi et al 1990;Turnham and Northcote 1983;Weselake et al 1993). Sulphur application (T2) increased the oil accumulation at all stages of seed development compared to -S+N treatment (T1).…”

“…Application of S (T2) increased the total sugar content at all the stages of seed development compared to -S treatment (T1). A reduction in total sugar content in treatment T1 was also observed previously (Ahmad et al, 2000;Fazli et al, 2005a;Munshi et al 1990). Acetyl-CoA carboxylase (acetyl-CoA: bicarbonate ligase [ATP], EC 6.4.1.2) catalyses the first committed step in the synthesis of fatty acids, i.e., carboxylation of acetyl-CoA to malonyl-CoA.…”

“…As a result, agricultural scientists are now recommending addition of S along with NPK for optimum productivity of mustard. Besides an improvement in the productivity of mustard, S fertilization also enhances the oil content of the seeds of oilseed crops (Abdin et al 2003;Ahmad and Abdin 2000a;Ahmad et al 2000;Asare and Scarisbrick 1995;Chaubey et al 1992;Chung et al 1995;Dubey et al 1994;Farahbakhsh et al 2006;Fazli et al 2005a, b;Jamal et al 2005Jamal et al , 2006Munshi et al 1990), indicating its role in oil biosynthesis. However, there is little data available to explain the effect of sulphur fertilization on oil biosynthesis and its related variables in the developing seeds of mustard.…”

Compositional changes in seeds influenced by their positions in different whorls of mature sunflower head

“…This result might be due to increased activities of α-and β-amylases in the former positions (data not shown). The accumulation of starch in sunflower 7 and other oilseeds 6,9,10 during seed development has already been well documented, and this starch is known to serve as a transient reserve material for the synthesis of storage lipids, ie triacylglycerols. Our recent study has shown that starch synthesis is biphasic in the seeds in the peripheral whorls in comparison with those in the middle and central whorls of the sunflower head, 11 which might contribute to better utilisation of starch for lipid biosynthesis.…”