Tissue Specificity of the Heat-Shock Response in Maize

Abstract

ABSTRACFThe tissue specificity of the heat-shock response is maize was investigated. The ability to synthesize heat shock proteins (hsp) at 40°C, as well as the intensity and duration of that synthesis, was analyzed in coleoptiles, scutella, green and etiolated leaves, snspensin-cultured cells, germinating pollen grains, and primary root section at different stages of development. One-dimensional sodium dodecyl sulfate gel electrophoresis of extracted proteins revealed that most of the tissues synthesized the typical set of 10 hsp, but that the exact charcterstics of the response depended upon the tissue type. While elongating portions of the primary root exhibited a strong heat shock response, the more mature portions showed a reduced ability to synthesize hsp. Leaves Higher plants have been shown to respond to elevated temperatures by synthesizing a set of hsp3 (1,5,11,18 In this report, the heat-shock response was investigated in a variety of maize tissues, including coleoptiles, scutella, green and etiolated leaves, suspension-cultured cells, germinating pollen gains, and primary roots at different stages of maturity. The ability ofthe tissue to synthesize hsp, as well as the intensity and duration of that synthesis, were analyzed. Also presented is evidence that hsp accumulate only to very low levels in maize. MATERIALS AND METHODSPlant Materials and Incubation Conditions. For studies involving roots, coleoptiles, scutella, and leaves, Crow's Hybrid No. 222 corn (Zea mays L., var A632 x C1042) was used. Roots coleoptiles were obtained from 3-d-old seedlings which had been germinated in darkness at 29°C in gla trays on paper towels kept moist with 0.1 mm CaCl2 solution. Scutella were from seeds imbibed for 24 h under similar conditions.Roots were excised and incubated in the manner previously described (11). Coleoptiles were separated from the rest of the plant, the 1-mm tip removed, and the 1 cm segment immediately below used for the experiment. The segment was longitudinally sliced in half, with one-half used as the control and the other half as the treatment. Half-segments from five plants were combined as a single sample and incubated in the major and minor salts of MS (27) medium as previously described (1 1). Scutella were isolated by aseptically removing the embryos from the seed and then dissecting out the embryonic axis. The scutella were incubated in pairs in a flask containing 2 ml MS salts. The flasks were shaken at 120 cycles/min in a constant temperature bath. The medium was replaced by 2 ml fresh MS salts at the appropriate temperature prior to addition of radioactive label. Unless otherwise stated, roots, coleoptiles, and scutella were incubated at 28°C for 4 h to allow them to overcome the shock of excision prior to any additional temperature treatment. All manipulations involving scutella and coleoptiles occurred in dim green light.For experiments involving leaves, seeds were planted in plastic dishpans in vermiculite and germinated in darkness at 29°C. Once the coleoptiles had emerged thro...

Synthesis of the Low Molecular Weight Heat Shock Proteins in Plants

“…The observation that maize synthesized and accumulated 24 low mol wt hsp is not consistent with previous reports (2,6 (22) and tobacco (19), would have to be resolved on a different gel system. Furthermore, Nover and Scharf (22) have detected minor hsp after enrichment of specific cellular fractions.…”

“…Pea had the greatest percentage (41%) detectable in control tissue. Although small amounts of some hsp have been reported in control tissue for tomato (22) and maize (6), detection of the low mol wt hsp in control seedlings was unexpected. In soybean, Northern analysis of poly(A)RNA from control seedlings failed to detect the presence of any mRNA for this group of proteins (7,13).…”

“…are reports that the low mol wt hsp are not synthesized in substantial quantities in maize (5,6). If the generalization that the low mol wt hsp are the major hsp in all plant species (12) is to hold true, then it would be expected that their synthesis is induced by hs and that they accumulate in all plant species.…”

“…Through twodimensional electrophoresis and fluorography, the low mol wt hsp have been shown to be comprised of a diverse array of polypeptides in several species (6,14,19,22,29). Although this group of proteins accumulates to stainable levels in tomato (22), soybean (1 1), cotton (4), and Tradescantia paludosa (29), there ' Supported through Department of Energy Contract #DE-AS09-80-ER 10678 to Joe L. Key.…”

Influence of Temperature Stress on in Vitro Fertilization and Heat Shock Protein Synthesis in Maize (Zea mays L.) Reproductive Tissues

“…This heat shock response has been observed in a wide variety of vegetative tissues in maize, including plumules (1), roots (4), coleoptiles, scutellum, leaves, and cultured cells (5).…”