Regulation of Legumin Levels in Developing Pea Seeds under Conditions of Sulfur Deficiency

Abstract

It was shown previously that when peas (Pisum sativum L.) are grown with suboptimal sulfur supply the level of legumin (the more S-rich of the two major seed storage proteins) in the mature seed is selectively reduced (Randall, Thomson, Schroeder, 1979 Aust J Plant Physiol 6: [11][12][13][14][15][16][17][18][19][20][21][22][23][24]. This paper reports a study of the cellular mechanisms involved in regulating legumin synthesis under these conditions. Pulse and pulse-chase labeling experiments were carried out with excised, immature cotyledons from normal and S-deficient plants. Legumin Legumin and vicilin are the two storage proteins accumulated in large quantities during the formation of pea (Pisum sativum L.) seeds. In the cultivar used in our experiments, legumin makes up approximately 15% of the total protein in the seed at maturity (25). Legumin has a higher content of cysteine and methionine than vicilin and could therefore be considered to be the more desirable protein from the point of view of animal nutrition. Its physicochemical properties are typical of one of the storage proteins found in a range of legume seeds including broad bean ( Vicia faba), lupin (Lupinus angustifolius), and soybean (Glycine max) (8).It was shown earlier (19) that when peas are grown with suboptimal sulfur (S) nutrition there is a marked, selective reduction in the level of accumulated legumin relative to the total protein level. Legumin was virtually undetectable under severe S deficiency. Similar changes were found in the more S-rich com-47 ponent of the storage proteins of lupin under S deficiency conditions (1).This paper describes experiments that were designed to study the cellular mechanisms responsible for the reduction in the level of legumin in pea seeds developing under conditions of S deficiency. The following three mechanisms were tested: (a) a normal rate of legumin synthesis but an increased rate of degradation; (b) a normal level of legumin mRNA but reduced translation; and (c) reduced levels of legumin mRNA. The results indicate that a reduced level of legumin mRNA is the main factor responsible for the reduced accumulation of legumin. MATERIALS AND METHODSPlant Material. Peas (Pisum sativum L.) line PI/G 086, selected from cv Greenfeast, were grown in artificially lit cabinets at 20°C with a 16-h photoperiod as described (16) and pods of a known age, specified as DAF 1, were used. Plants were grown in sand with nutrient solution containing combined nitrogen (19). Sulfur was supplied as MgSO4 at I mm in the control nutrient throughout growth and 0.05 mm in the S-deficient nutrient until first flower and omitted thereafter. The level of Mg2+ was kept constant by varying MgCl2. Under these conditions, S-deficient plants showed characteristic symptoms and were smaller with fewer pods. Mean seed weight at maturity was little affected in pods from lower nodes but considerably reduced in later formed pods. For uniformity, only pods from the third to the sixth flowering node were used. Mature seeds from t...

Effects of Nutritional Stress on the Storage Proteins of Soybeans

“…Since it has been shown (8) that each ofthe subunits of(3-conglycinin is coded for by separate mRNAs, it would be possible for such specific regulation to occur in the same way as described for regulation of legumin in peas in response to equivalent sulfur deficiency. In peas, sulfur deficiency caused alteration in the level of legumin-specific mRNA (1). It is probable that both the modifications to the ,8-conglycinins and also the other alterations induced by sulfur deficiency, both within the glycinin family and of the protein of apparent Mr 91,000, all reflect similar alterations in specific mRNA levels.…”

“…In both lupin (3) and peas (7), sulfur deficiency specifically depressed the synthesis of particular sulfur-rich proteins. In peas, sulfur deficiency operated specifically by repression of the levels of legumin mRNA (1).…”

Expression of XET‐related genes and its relation to elongation in leaves of barley (Hordeum vulgare L.)

“…DNA was washed with 70% ethanol, dried under vacuum, resuspended in 300 mm' TE, and then digested overnight with each restriction enzyme, and 25 pg per lane was clcctr-ophor-e.scd in agar'o.se gels and capillar-y-blotted onto nylon rnernbrarie. Hybridization and washing wer-e car--ried out as described pr-eviously (Chandler et al 1983). Einal wash conditions were 0-1 x SSC, 0-5% SDS at 50 °C.…”

Bean [alpha]-Amylase Inhibitor Confers Resistance to the Pea Weevil (Bruchus pisorum) in Transgenic Peas (Pisum sativum L.)

“…The total RNA fraction was isolated (Chandler et al, 1983) from pooled, developing T, pea seecls (22-25 DAF) from the selected primary transformants, fractionated by electrophoresis, blotted, and probed with aai DNA as above (Higgins and Spencer, 1991).…”