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Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

After reproduction is initiated in plants, subsequent reproductive development is sometimes interrupted, which decreases the final number of seeds and fruits. We subjected maize (Zea mays L.) to low water potentials (psi(w)) that frequently cause this kind of failure. We observed metabolite pools and enzyme activities in the developing ovaries while we manipulated the sugar stream by feeding sucrose (Suc) to the stems. Low psi(w) imposed for 5 d around pollination allowed embryos to form, but abortion occurred and kernel number decreased markedly. The ovary contained starch that nearly disappeared during this abortion. Analyses showed that all of the intermediates in starch synthesis were depleted. However, when labeled Suc was fed to the stems, label arrived at the ovaries. Solute accumulated and caused osmotic adjustment. Suc accumulated, but other intermediates did not, showing that a partial block in starch synthesis occurred at the first step in Suc utilization. This step was mediated by invertase, which had low activity. Because of the block, Suc feeding only partially prevented starch disappearance and abortion. These results indicate that young embryos abort when the sugar stream is interrupted sufficiently to deplete starch during early ovary development, and this abortion results in a loss of mature seeds and fruits. At low psi(w), maintaining the sugar stream partially prevented the abortion, but invertase regulated the synthesis of ovary starch and partially prevented full recovery.
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PMID:Starch and the control of kernel number in maize at low water potentials. 1048 57

Water deficit during meiosis in pollen mother cells of wheat (Triticum aestivum L.) induces male sterility, which can reduce grain set by 40 to 50%. In plants stressed during meiosis and then rewatered, division of pollen mother cells proceeds normally but subsequent pollen development is arrested 3 or 4 d later. An inhibition of starch accumulation within the pollen grain suggested that an alteration in carbohydrate metabolism or assimilate supply may be involved in pollen abortion. We measured levels of various carbohydrates and activities of key enzymes of Suc metabolism and starch synthesis at different stages of pollen development in anthers collected from well-watered and water-stressed plants. Compared to controls, soluble sugars increased in anthers stressed during meiosis, then decreased at later poststress stages. Sucrose and myoinositol accounted for part of the sugar accumulation. The activity of soluble acid invertase declined 4-fold during the stress period and never recovered thereafter. Sucrose synthase activity during starch accumulation in pollen was also lower in the anthers of plants stressed at meiosis. Stress had little negative effect on the activities of ADP-glucose pyrophosphorylase or soluble and granule-bound starch synthase during starch accumulation in pollen, although at the earlier stages, ADP-glucose pyrophosphorylase activity in stressed anthers was slightly lower compared to controls. The results suggest that carbohydrate starvation per se and inhibition of the enzymes of starch synthesis probably were not responsible for the stress-induced pollen abortion. Instead, an inability to metabolize incoming sucrose to hexoses may be involved in this developmental lesion.
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PMID:Induction of Male Sterility in Wheat by Meiotic-Stage Water Deficit Is Preceded by a Decline in Invertase Activity and Changes in Carbohydrate Metabolism in Anthers. 1222 80

Water deficit during pollination increases the frequency of kernel abortion in maize (Zea mays L.). Much of the kernel loss is attributable to lack of current photosynthate, but a large number of kernels fail to develop on water-deficient plants even when assimilate supply is increased. We examined the possibility that assimilate utilization by developing ovaries might be impaired at low water potential ([Psi]w). Plants were grown in the greenhouse in 20-L pots containing 22 kg of amended soil. Water was withheld on the first day silks emerged, and plants were hand-pollinated 4 d later when leaf [Psi]w decreased to approximately - 1.8 MPa and silk [Psi]w was approximately -1.0 MPa. Plants were rehydrated 2 d after pollination. The brief water deficit inhibited ovary growth (dry matter accumulation) and decreased kernel number per ear by 60%, compared to controls. Inhibition of ovary growth was associated with a decrease in the level of reducing sugars, depletion of starch, a 75-fold increase in sucrose concentration (dry weight basis), and inhibition of acid invertase (EC 3.2.1.26) activity. These results indicate that water deficits during pollination disrupt carbohydrate metabolism in maize ovaries. They suggest that acid invertase activity is important for establishing and maintaining reproductive sink strength during pollination and early kernel development.
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PMID:Low Water Potential Disrupts Carbohydrate Metabolism in Maize (Zea mays L.) Ovaries. 1222 65

To distinguish their roles in early kernel development and stress, expression of soluble (Ivr2) and insoluble (Incw2) acid invertases was analyzed in young ovaries of maize (Zea mays) from 6 d before (-6 d) to 7 d after pollination (+7 d) and in response to perturbation by drought stress treatments. The Ivr2 soluble invertase mRNA was more abundant than the Incw2 mRNA throughout pre- and early post-pollination development (peaking at +3 d). In contrast, Incw2 mRNAs increased only after pollination. Drought repression of the Ivr2 soluble invertase also preceded changes in Incw2, with soluble activity responding before pollination (-4 d). Distinct profiles of Ivr2 and Incw2 mRNAs correlated with respective enzyme activities and indicated separate roles for these invertases during ovary development and stress. In addition, the drought-induced decrease and developmental changes of ovary hexose to sucrose ratio correlated with activity of soluble but not insoluble invertase. Ovary abscisic acid levels were increased by severe drought only at -6 d and did not appear to directly affect Ivr2 expression. In situ analysis showed localized activity and Ivr2 mRNA for soluble invertase at sites of phloem-unloading and expanding maternal tissues (greatest in terminal vascular zones and nearby cells of pericarp, pedicel, and basal nucellus). This early pattern of maternal invertase localization is clearly distinct from the well-characterized association of insoluble invertase with the basal endosperm later in development. This localization, the shifts in endogenous hexose to sucrose environment, and the distinct timing of soluble and insoluble invertase expression during development and stress collectively indicate a key role and critical sensitivity of the Ivr2 soluble invertase gene during the early, abortion-susceptible phase of development.
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PMID:Soluble invertase expression is an early target of drought stress during the critical, abortion-sensitive phase of young ovary development in maize. 1237 27

Plant reproduction is sensitive to water deficits, especially during the early phases when development may cease irreversibly even though the parent remains alive. Grain numbers decrease because of several developmental changes, especially ovary abortion in maize (Zea mays L.) or pollen sterility in small grains. In maize, the water deficits inhibit photosynthesis, and the decrease in photosynthate flux to the developing organs appears to trigger abortion. Abscisic acid also increases in the parent and may play a role, perhaps by inhibiting photosynthesis through stomatal closure. Recent work indicates that invertase activity is inhibited and starch is diminished in the ovaries or affected pollen. Also, sucrose fed to the stems rescues many of the ovaries otherwise destined to abort. The feeding restores some of the ovary starch and invertase activity. These studies implicate invertase as a limiting enzyme step for grain yields during a water deficit, and transcript profiling with microarrays has identified genes that are up- or down-regulated during water deficit-induced abortion in maize. However, profiling studies to date have not reported changes in invertase or starch synthesizing genes in water-deficient ovaries, perhaps because there were too few sampling times. The ovary rescue with sucrose feeding indicates either that the changes identified in the profiling are of no consequence for inhibiting ovary development or that gene expression reverts to control levels when the sugar stream recovers. Careful documentation of tissue- and developmentally specific gene expression are needed to resolve these issues and link metabolic changes to the decreased sugar flux affecting the reproductive organs.
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PMID:Grain yields with limited water. 1528 47

In many situations, organisms respond to stimuli by altering the activity of large numbers of genes. Among these, certain ones are likely to control the phenotype while others play a secondary role or are passively altered without directly affecting the phenotype. Identifying the controlling genes has proven difficult. However, in a few instances, it has been possible to reverse the phenotype by physiological or biochemical means without altering the genetics of the organism. During this functional reversion, only a few genes may respond, thus identifying those likely to be controlling the phenotype. Floral abortion during a water shortage in maize is an example because the response is inherently multigenic, and the phenotype can be reversed by physiological/biochemical means. A recent analysis used this reversal to reveal that only a few genes are likely to control the abortion phenotype. In maize, these genes coded for a cell wall invertase (Incw2), a soluble invertase (Ivr2), a ribosome-inactivating protein (RIP2), and phospholipase D (PLD1). The invertases appeared to control the normal sugar uptake by the ovaries. Their down-regulation depleted ovary sugar pools and resulted in an up-regulation of the genes for ribosome-inactivating protein and for phospholipase. The latter changes appeared to initiate senescence that degraded cell membranes, thus causing irreversible abortion. With these findings, these genes have become targets for preventing abortion. This approach might have value in other contexts with some additional methods.
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PMID:Functional reversion to identify controlling genes in multigenic responses: analysis of floral abortion. 1710 69

It has been previously demonstrated, utilizing intraspecific introgression lines, that Lycopersicum Invertase5 (LIN5), which encodes a cell wall invertase, controls total soluble solids content in tomato (Solanum lycopersicum). The physiological role of this protein, however, has not yet been directly studied, since evaluation of data obtained from the introgression lines is complicated by the fact that they additionally harbor many other wild species alleles. To allow a more precise comparison, we generated transgenic tomato in which we silenced the expression of LIN5 using the RNA interference approach. The transformants were characterized by an altered flower and fruit morphology, displaying increased numbers of petals and sepals per flower, an increased rate of fruit abortion, and a reduction in fruit size. Evaluation of the mature fruit revealed that the transformants were characterized by a reduction of seed number per plant. Furthermore, detailed physiological analysis revealed that the transformants displayed aberrant pollen morphology and a reduction in the rate of pollen tube elongation. Metabolite profiling of ovaries and green and red fruit revealed that metabolic changes in the transformants were largely confined to sugar metabolism, whereas transcript and hormone profiling revealed broad changes both in the hormones themselves and in transcripts encoding their biosynthetic enzymes and response elements. These results are discussed in the context of current understanding of the role of sugar during the development of tomato fruit, with particular focus given to its impact on hormone levels and organ morphology.
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PMID:RNA interference of LIN5 in tomato confirms its role in controlling Brix content, uncovers the influence of sugars on the levels of fruit hormones, and demonstrates the importance of sucrose cleavage for normal fruit development and fertility. 1943 74

To examine the difference between early kernels at different ear position in maize and the effect of nitrogen supply rates on kernel development, physiological indices in apical and mid-basal kernel 5-20 days after pollination in maize under different nitrogen supply rates (0, 120, 180 and 240 kg x ha(-1)) were determined with UV-Vis spectrophotometry. The results showed that nitrogen supply obviously increased the contents of soluble sugar, sucrose and starch, and the activities of enzymes related to sucrose inversion and starch synthesis. Twenty days after pollination, the kernel volume, dry weight and the contents of soluble sugar, sucrose and starch in apical kernel under nitrogen supply rate of 180 kg x ha(-1) were higher than those with other treatments. Five to twenty days after pollination, higher activities of acid sucrose invertase (AI), neutral sucrose invertase (NI), sucrose synthase (SS), ADPGase and starch synthase in apical kernel were also obtained under nitrogen supply rate of 180 kg x ha(-1), indicating that the sucrose utilization and starch synthesis were improved, the kernel development was promoted and the kernel abortion was reduced, which resulted in higher yield.
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PMID:[Determination of physiological indices in early kernel at different ear position in maize (Zea mays L.) with UV-visible spectrophotometry]. 1995 Jun 73

Reproductive stage water stress leads to spikelet sterility in wheat. Whereas drought stress at anthesis affects mainly grain size, stress at the young microspore stage of pollen development is characterized by abortion of pollen development and reduction in grain number. We identified genetic variability for drought tolerance at the reproductive stage. Drought-tolerant wheat germplasm is able to maintain carbohydrate accumulation in the reproductive organs throughout the stress treatment. Starch depletion in the ovary of drought-sensitive wheat is reversible upon re-watering and cross-pollination experiments indicate that the ovary is more resilient than the anther. The effect on anthers and pollen fertility is irreversible, suggesting that pollen sterility is the main cause of grain loss during drought conditions in wheat. The difference in storage carbohydrate accumulation in drought-sensitive and drought-tolerant wheat is correlated with differences in sugar profiles, cell wall invertase gene expression and expression of fructan biosynthesis genes in anther and ovary (sucrose : sucrose 1-fructosyl-transferase, 1-SST; sucrose : fructan 6-fructosyl-transferase, 6-SFT). Our results indicate that the ability to control and maintain sink strength and carbohydrate supply to anthers may be the key to maintaining pollen fertility and grain number in wheat and this mechanism may also provide protection against other abiotic stresses.
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PMID:Importance of pre-anthesis anther sink strength for maintenance of grain number during reproductive stage water stress in wheat. 2019 26

Drought stress affects cereals especially during the reproductive stage. The maize (Zea mays) drought transcriptome was studied using RNA-Seq analysis to compare drought-treated and well-watered fertilized ovary and basal leaf meristem tissue. More drought-responsive genes responded in the ovary compared with the leaf meristem. Gene Ontology enrichment analysis revealed a massive decrease in transcript abundance of cell division and cell cycle genes in the drought-stressed ovary only. Among Gene Ontology categories related to carbohydrate metabolism, changes in starch and Suc metabolism-related genes occurred in the ovary, consistent with a decrease in starch levels, and in Suc transporter function, with no comparable changes occurring in the leaf meristem. Abscisic acid (ABA)-related processes responded positively, but only in the ovaries. Related responses suggested the operation of low glucose sensing in drought-stressed ovaries. The data are discussed in the context of the susceptibility of maize kernel to drought stress leading to embryo abortion and the relative robustness of dividing vegetative tissue taken at the same time from the same plant subjected to the same conditions. Our working hypothesis involves signaling events associated with increased ABA levels, decreased glucose levels, disruption of ABA/sugar signaling, activation of programmed cell death/senescence through repression of a phospholipase C-mediated signaling pathway, and arrest of the cell cycle in the stressed ovary at 1 d after pollination. Increased invertase levels in the stressed leaf meristem, on the other hand, resulted in that tissue maintaining hexose levels at an "unstressed" level, and at lower ABA levels, which was correlated with successful resistance to drought stress.
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PMID:Effects of drought on gene expression in maize reproductive and leaf meristem tissue revealed by RNA-Seq. 2283 60


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