Water Deficits and Reproduction in Maize

Westgate, Mark E.; Grant, Debra L. Thomson

doi:10.1104/pp.91.3.862

Cited by 62 publications

(14 citation statements)

References 20 publications

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“…For example, in vitro growth conditions may induce the synthesis and accumulation of ABA due to a more negative 4t' than exists in vivo. In addition, a decrease in i1, can alter the growth potential of maize kernels by prematurely accelerating grain desiccation (24). Hastened development was also indicated in the current study, because the cell division rates declined earlier in kemels cultured in low 14' media than in the control (Fig.…”

Section: Discussionsupporting

confidence: 69%

Endosperm Cell Division in Maize Kernels Cultured at Three Levels of Water Potential

Myers¹,

Setter²,

Madison³

et al. 1992

Plant Physiol.

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The influence of osmoticum treatments on early kernel development of maize (Zea mays L.) was studied using an in vitro culture method. Kernels with subtending cob sections were placed in culture at 5 days after pollination. Sucrose (0.29, 0.44, or 0.58 molar) and sorbitol (0, 0.15, or 0.29 molar) were used to obtain six media with water potentials of -1.1, -1.6, or -2.0 megapascals. Kernel water potential declined in correspondence with the water potential of the medium; however, fresh weight growth was not significantly inhibited from 5 to 12 days after pollination. In stress treatments with media water potentials of -1.6 or -2.0 megapascals, endosperm tissue accumulated water and solutes from 10 and 12 days after pollination at a rate similar to or greater than that of the control (-1.1 megapascals). In contrast, endosperm cell division was inhibited in all treatments relative to control. At 10 days after pollination, endosperm sucrose concentration was greater in two of the -2.0 megapascal treatments with 0.44 or 0.58 molar media sucrose compared to control kernels cultured in 0.29 molar sucrose at -1.1 megapascals. Significant increases in abscisic acid content per gram of fresh weight were detected in two -2.0 megapascal treatments (0.29 molar sucrose plus 0.29 molar sorbitol and 0.58 molar sucrose) at 10 days after pollination. We conclude that in cultured maize kernels, endosperm cell division was more responsive than fresh weight accumulation to low water potential treatments. Data were consistent with mechanisms involving abscisic acid or lowered tissue water potential, or an interaction of the two factors.also be considered (reviewed by Kermode [11]). Perhaps the effects of ABA observed on endosperm cell division could be duplicated or attenuated by altered solute concentration. In support of this possibility, studies have shown that the effects of ABA on embryo development can be mimicked to some extent by increased solute concentration (1,4,12). However, in some systems, such responses to solute concentration require a concomitant rise in endogenous ABA (21,25). Thus, to evaluate the effects of water deficit on endosperm development, both tissue water status (0', r, Op) and ABA levels need to be considered.In maize kemel culture, the level of carbohydrates available to the developing kemel is controlled by medium composition. In this study, we altered the i, of the medium by adding increments of sucrose and/or sorbitol. Sorbitol was used to impose the /w treatments in an attempt to separate the effects of increased carbohydrate nutrition from the effects of decreased 0,. Individual kemels with a small piece of subtending cob tissue were placed on the media and cultured for 3 to 7 d. This method excludes most matemal tissue, thereby decreasing import of ABA from leaves and roots. The goals of the present studies were to assess the extent to which endosperm cell division and FW accumulation respond to elevated osmoticum concentration and to evaluate the potential role of changes in tissue wat...

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Section: Discussionsupporting

confidence: 69%

Endosperm Cell Division in Maize Kernels Cultured at Three Levels of Water Potential

Myers¹,

Setter²,

Madison³

et al. 1992

Plant Physiol.

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“…Similarly, in a field study of container-grown maize, no difference in kernel ,t, was found between control and water-limited plants, sampled as early as 6 days after anthesis (30). Other studies of maize have suggested that the effect of water deficit on kernel {4K may be greater at early stages of development (43). When water was withheld beginning at anthesis, K , 6 of unpollinated ovaries decreased from -0.5 to -1.0 MPa over a 6-d period, whereas midday 4', of leaves decreased from -0.5 to -1.75 MPa (43).…”

Section: Kernel Water Potentialmentioning

confidence: 88%

Influence of Water Deficit on Maize Endosperm Development

Ober¹,

Setter²,

Madison³

et al. 1991

Plant Physiol.

132

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In maize (Zea mays L.), drought during the post-pollination stage decreases kernel growth and often leads to grain yield losses. Kernels in the apical region of the ear are more severely affected than basally positioned kernels. We hypothesized that water deficit during early endosperm development might inhibit kernel growth by decreasing endosperm cell division, and that this response might be mediated by changes in endosperm abscisic acid (ABA) levels. Greenhouse-grown maize, cultivar Pioneer 3925, was subjected to water limitation from 1 to 15 days after pollination (DAP), spanning the period of endosperm cell division and induction of storage product accumulation. Water deficit decreased the number of endosperm nuclei during the treatment period; the most substantial effect was in the apical region of ears. Correspondingly, endosperm fresh weight, starch accumulation and dry mass at maturity were decreased by water limitation. Abscisic acid concentrations in endosperm were quantified by enzyme-linked immunosorbent assay. Water deficit increased ABA concentration in apical-region endosperm by fourfold compared to controls. ABA concentrations were also increased in middle and basal regions of the ear, but to a lesser extent. Two key enzymes in the starch synthesis pathway, sucrose synthase and granule-bound ADP-glucose starch synthase, and zein, the major storage protein in maize endosperm, were studied as markers of storage product synthesis. Water deficit did not affect sucrose synthase enzyme activity or RNA transcript abundance relative to total RNA. However, ADP-glucose starch synthase activity and RNA transcript abundance decreased slightly in apical-region endosperm of water-limited plants by 15 DAP, compared with well-watered controls. In contrast to starch, there was no treatment effect on the accumulation of zein, evaluated at either the polypeptide or RNA level. We conclude that under the conditions tested, the establishment of starch and zein synthetic potential in endosperm was only slightly affected by plant water deficit during the early phase of kernel growth, and that capacity for growth and starch accumulation was affected by the extent to which cell division was inhibited. Based on correlative changes in ABA concentration and cell division we suggest that ABA may play a role in inhibiting endosperm cell division during water limitation.

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“…Whereas placenta is highly vascularized such that its water status can equilibrate with whole-plant water potential during a stress episode, endosperm is remote from vasculature and is hydraulically isolated to some extent. Such isolation was documented in studies where whole-plant water deficit substantially lowered water potential in leaves and floral tissues, whereas water potentials of whole maize kernels or embryos remained the same as controls (Westgate and Thomson Grant, 1989;Ober and Setter, 1990). Steep downhill gradients in water potential were found from pedicel phloem to the grain in wheat (Triticum aestivum), consistent with hydraulic isolation between vasculature and surrounding tissues (Fisher and CashClark, 2000).…”

Section: Placenta and Endosperm Respond Differently To Water Deficit mentioning

confidence: 90%

“…Stresses that occur soon after pollination coincide with the period of endosperm cell division. This phase is particularly sensitive to water deficit, whereas later phases of kernel development, when starch and zein synthesis are at their maximum, are usually less affected (Grant et al, 1989;Artlip et al, 1995;Mambelli and Setter, 1998). Water deficit during the first few days after pollination inhibits endosperm cell proliferation, which is well correlated with kernel size at maturity (Nicolas et al, 1985;Ober et al, 1991).…”

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confidence: 99%

Comparative Transcriptional Profiling of Placenta and Endosperm in Developing Maize Kernels in Response to Water Deficit

Setter

2003

Plant Physiology

147

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The early post-pollination phase of maize (Zea mays) development is particularly sensitive to water deficit stress. Using cDNA microarray, we studied transcriptional profiles of endosperm and placenta/pedicel tissues in developing maize kernels under water stress. At 9 d after pollination (DAP), placenta/pedicel and endosperm differed considerably in their transcriptional responses. In placenta/pedicel, 79 genes were significantly affected by stress and of these 89% were up-regulated, whereas in endosperm, 56 genes were significantly affected and 82% of these were down-regulated. Only nine of the stress-regulated genes were in common between these tissues. Hierarchical cluster analysis indicated that different sets of genes were regulated in the two tissues. After rewatering at 9 DAP, profiles at 12 DAP suggested that two regulons exist, one for genes responding specifically to concurrent imposition of stress, and another for genes remaining affected after transient stress. In placenta, genes encoding recognized stress tolerance proteins, including heat shock proteins, chaperonins, and major intrinsic proteins, were the largest class of genes regulated, all of which were up-regulated. In contrast, in endosperm, genes in the cell division and growth category represented a large class of down-regulated genes. Several cell wall-degrading enzymes were expressed at lower levels than in controls, suggesting that stress delayed normal advance to programmed cell death in the central endosperm. We suggest that the responsiveness of placenta to whole-plant stress factors (water potential, abscisic acid, and sugar flux) and of endosperm to indirect factors may play key roles in determining the threshold for kernel abortion.Water deficit during pollination and grain formation causes severe losses in crop production. In maize (Zea mays), the early reproductive stages of kernel development have long been recognized as being particularly vulnerable to water deficit (Claassen and Shaw, 1970); however, the mechanistic bases of cellular response are still not fully understood. Stresses that occur soon after pollination coincide with the period of endosperm cell division. This phase is particularly sensitive to water deficit, whereas later phases of kernel development, when starch and zein synthesis are at their maximum, are usually less affected (Grant et al., 1989; Artlip et al., 1995; Mambelli and Setter, 1998). Water deficit during the first few days after pollination inhibits endosperm cell proliferation, which is well correlated with kernel size at maturity (Nicolas et al., 1985; Ober et al., 1991). During this period, the development of placenta and vascular tissue of the pedicel creates capacity for influx of sugar and signaling molecules. Such development also occurs during the late phases of floral growth, which is also highly sensitive to stresses (Otegui et al., 1995; Edmeades et al., 2000).Previous studies of maize have indicated that reproductive abortion in stress environments involves the plant hormone abscisic a...

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Water Deficits and Reproduction in Maize

Cited by 62 publications

References 20 publications

Endosperm Cell Division in Maize Kernels Cultured at Three Levels of Water Potential

Endosperm Cell Division in Maize Kernels Cultured at Three Levels of Water Potential

Influence of Water Deficit on Maize Endosperm Development

Comparative Transcriptional Profiling of Placenta and Endosperm in Developing Maize Kernels in Response to Water Deficit

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