Yield maintenance under drought: expansive growth and hydraulics also matter in reproductive organs

Yield maintenance under drought in maize (Zea mays) is associatedwith flowering synchrony which requires the rapid extensionof styles and stigma (silks) to be accessible for pollen. Wehave shown that the control of grain set under moderate waterdeficits similar to those in the field result from a developmentalprocess linked to the timing of silk growth, in opposition to thecommon view that abortion is linked to the sugar metabolismin ovaries. A switch to abortion occurs 2-3 days after first silkemergence in water-stressed plants, when silk growth stops simultaneouslyfor all ovary cohorts, and explains abortion rates indifferent treatments, genotypes and positions on the ear. Analysesof transcripts and metabolites indicate that the first molecularevents occur in silks rather than in ovaries, and involve genesaffecting expansive growth rather than sugar metabolism. Sugaravailability is preserved in ovaries until the switch to abortion,and the disruption of carbon metabolism only occurs afterwards.Hence, changes in metabolite contents, transcript amounts andenzyme activities involved in ovary sugar metabolism would bea consequence rather than a cause of the beginning of ovaryabortion. Patterns of silk growth responses to environment sharecommon features with those of leaf growth, with both kineticand genetic evidences. These findings have large consequencesfor breeding drought tolerant maize and for modelling grainyields under drought. Oury et al (2016) Plant Physiology171: 986-996 and 171: 997-1008Turc et al (2016) New Phytologist 212: 377–38

Seed abortion of maize under water deficit is linked to a developmental process and not to carbon deprivation

Seed abortion is a major cause of yield loss under water deficit in maize, thereby causing a high sensitivity of maize yield to droughts occurring at flowering time. It is usually believed that drough-tinduced seed abortion is linked to sugar deprivation because sugar feeding can relieve part of the effect of water deficit. However, the experiments that evidenced this effect involved very severe deficit, not compatible with those sensed by most plants in the field. In our experiments, a field-compatible water deficit (predawn leaf water potential of 0.4 MPa) caused 30 to 50% abortion, involving ovules located near the ear tip. Sucrose and hexose concentrations were unaffected or slightly increased by water deficit in ovules located either in the base or in the tip of ears, at four dates around silking. Activities of major enzymes, measured in the young ovules, were essentially unaffected, with a slight increase and decrease in SPS and invertase activities, respectively, under water deficit. It is therefore unlikely that tip abortion in moderate water deficit is linked to sugar deprivation. We propose an alternative mechanism based on the gradient of development within the ear. Silks are initiated with a basetip gradient of age, so the first silks to emerge are the oldest, located at the base of the ear. Our current research strongly suggests that abortion in water deficit is related to the timing of silk emergence. The latter is delayed under water deficit, so a longer period of time elapses from the first to the last silk emergence. This developmental process would explain both phenotypic variations with water deficit within a given genotype, and the difference in sensitivity between genotypes.Drought-tolerant yielding plant

Yield maintenance under drought: expansive growth and hydraulics also matter in reproductive organs

Yield maintenance under drought in maize (Zea mays) is associatedwith flowering synchrony which requires the rapid extensionof styles and stigma (silks) to be accessible for pollen. Wehave shown that the control of grain set under moderate waterdeficits similar to those in the field result from a developmentalprocess linked to the timing of silk growth, in opposition to thecommon view that abortion is linked to the sugar metabolismin ovaries. A switch to abortion occurs 2-3 days after first silkemergence in water-stressed plants, when silk growth stops simultaneouslyfor all ovary cohorts, and explains abortion rates indifferent treatments, genotypes and positions on the ear. Analysesof transcripts and metabolites indicate that the first molecularevents occur in silks rather than in ovaries, and involve genesaffecting expansive growth rather than sugar metabolism. Sugaravailability is preserved in ovaries until the switch to abortion,and the disruption of carbon metabolism only occurs afterwards.Hence, changes in metabolite contents, transcript amounts andenzyme activities involved in ovary sugar metabolism would bea consequence rather than a cause of the beginning of ovaryabortion. Patterns of silk growth responses to environment sharecommon features with those of leaf growth, with both kineticand genetic evidences. These findings have large consequencesfor breeding drought tolerant maize and for modelling grainyields under drought. Oury et al (2016) Plant Physiology171: 986-996 and 171: 997-1008Turc et al (2016) New Phytologist 212: 377–38

Analysis of enzyme activities

The evaluation of enzyme activities, especially their capacities, represents an important step towards the modelling of biochemical pathways in living organisms. The implementation of microplate technology enables the determination of up to >50 enzymes in relatively large numbers of samples and in various biological materials. Most of these enzymes are involved in central metabolism and several pathways are entirely covered. Direct or indirect assays can be used, as well as highly sensitive assays, depending on the abundance of the enzymes under study. To exemplify such methods, protocols for UDP-glucose pyrophosphorylase (E.C. 2.7.7.9) operating in real time and for pyrophosphate:fructose-6-phosphate 1-phosphotransferase (E.C. 2.7.1.90) are presented

Seed abortion of maize under water deficit is linked to a developmental process and not to carbon deprivation

Seed abortion is a major cause of yield loss under water deficit in maize, thereby causing a high sensitivity of maize yield to droughts occurring at flowering time. It is usually believed that drough-tinduced seed abortion is linked to sugar deprivation because sugar feeding can relieve part of the effect of water deficit. However, the experiments that evidenced this effect involved very severe deficit, not compatible with those sensed by most plants in the field. In our experiments, a field-compatible water deficit (predawn leaf water potential of 0.4 MPa) caused 30 to 50% abortion, involving ovules located near the ear tip. Sucrose and hexose concentrations were unaffected or slightly increased by water deficit in ovules located either in the base or in the tip of ears, at four dates around silking. Activities of major enzymes, measured in the young ovules, were essentially unaffected, with a slight increase and decrease in SPS and invertase activities, respectively, under water deficit. It is therefore unlikely that tip abortion in moderate water deficit is linked to sugar deprivation. We propose an alternative mechanism based on the gradient of development within the ear. Silks are initiated with a basetip gradient of age, so the first silks to emerge are the oldest, located at the base of the ear. Our current research strongly suggests that abortion in water deficit is related to the timing of silk emergence. The latter is delayed under water deficit, so a longer period of time elapses from the first to the last silk emergence. This developmental process would explain both phenotypic variations with water deficit within a given genotype, and the difference in sensitivity between genotypes.Drought-tolerant yielding plant

Grain abortion under drought in maize: expansive growth and hydraulics also matter

Yield maintenance under drought in maize (Zea mays) requires the rapid extension of styles and stigma (silks) that collect pollen. We have shown that the control of grain set under moderate water deficits similar to those in the field result from a developmental process linked to the timing of silk growth, in opposition to the common view that abortion is linked to the sugar metabolism in ovaries. A switch to abortion occurs 2-3d after first silk emergence in water-stressed plants, when silk growth stops simultaneously for all ovary cohorts, and explains abortion rates in different treatments and positions on the ear. Analyses of transcripts and metabolites indicate that the first molecular events occur in silks rather than in ovaries, and involve genes affecting expansive growth rather than sugar metabolism. Sugar availability is preserved in ovaries until the switch to abortion, and the disruption of carbon metabolism only occurs afterwards. Hence, changes in metabolite contents, transcript amounts and enzyme activities involved in ovary sugar metabolism would be a consequence rather than a cause of the beginning of ovary abortion. Patterns of silk growth responses to environment share common features with those of leaf growth with both kinetic and genetic evidences. These findings have large consequences for breeding drought tolerant maize and for modelling grain yields under drought.Développer de nouvelles variétés de maïs pour une agriculture durable: une approche intégrée de la génomique à la sélectionDrought-tolerant yielding plant

Grain abortion under drought in maize: expansive growth and hydraulics also matter

Yield maintenance under drought in maize (Zea mays) requires the rapid extension of styles and stigma (silks) that collect pollen. We have shown that the control of grain set under moderate water deficits similar to those in the field result from a developmental process linked to the timing of silk growth, in opposition to the common view that abortion is linked to the sugar metabolism in ovaries. A switch to abortion occurs 2-3d after first silk emergence in water-stressed plants, when silk growth stops simultaneously for all ovary cohorts, and explains abortion rates in different treatments and positions on the ear. Analyses of transcripts and metabolites indicate that the first molecular events occur in silks rather than in ovaries, and involve genes affecting expansive growth rather than sugar metabolism. Sugar availability is preserved in ovaries until the switch to abortion, and the disruption of carbon metabolism only occurs afterwards. Hence, changes in metabolite contents, transcript amounts and enzyme activities involved in ovary sugar metabolism would be a consequence rather than a cause of the beginning of ovary abortion. Patterns of silk growth responses to environment share common features with those of leaf growth with both kinetic and genetic evidences. These findings have large consequences for breeding drought tolerant maize and for modelling grain yields under drought

Régulation de la synthèse des protéines de réserve du grain de blé en réponse à la disponibilité en azote et soufre

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