Abstract
The common bean (Phaseolus vulgaris L.) low phytic acid (lpa1) biofortified genotype produces seeds with improved nutritional characteristics and does not display negative pleiotropic effects. Here we demonstrated that lpa1 plants establish an efficient nitrogen-fixing symbiosis with Rhizobium etli CE3. The lpa1 nodules showed a higher expression of nodule-function related genes than the nodules of the parental wild type genotype (BAT 93). We analyzed the response to water stress of lpa1 vs. BAT 93 plants grown under fertilized or under symbiotic N2-fixation conditions. Water stress was induced by water withholding (up to 14% soil moisture) to fertilized or R. etli nodulated plants previously grown with normal irrigation. The fertilized lpa1 plants showed milder water stress symptoms during the water deployment period and after the rehydration recovery period when lpa1 plants showed less biomass reduction. The symbiotic water-stressed lpa1 plants showed decreased nitrogenase activity that coincides with decreased sucrose synthase gene expression in nodules; lower turgor weight to dry weight (DW) ratio, which has been associated with higher drought resistance index; downregulation of carbon/nitrogen (C/N)-related and upregulation of stress-related genes. Higher expression of stress-related genes was also observed in bacteroids of stressed lpa1 plants that also displayed very high expression of the symbiotic cbb3 oxidase (fixNd).
Highlights
Common bean (Phaseolus vulgaris L.) is the world’s most important food legume; it provides up to15% of total daily calories and 36% of total daily proteins in different regions of Africa and Americas.As a legume, common bean can establish symbiosis with soil bacteria known as rhizobia to capture atmospheric N2 and thereby to support plant growth
Previous data obtained by our group indicated that the agronomic performance of the common datamutant obtainedwas by our indicated the agronomic performance of theThe common bean lpa1Previous biofortified notgroup affected whenthat grown in field conditions biological bean lpa1 biofortified mutant was not affected when grown in field conditions
It is well known that phytic acid is an important molecule for seed phosphorus storage, but, together with its precursors and its derivative molecules (InsP7 and InsP8 inositol pyrophosphates), it has an important role in regulation of different cell signaling and plant processes, including signal transduction, sugar signaling, storage and polar transport of auxin, membrane trafficking, abiotic and biotic stress response, phosphorus homeostasis, photomorphogenesis, chromatin modification and remodeling and mRNA nuclear export [21]
Summary
Common bean (Phaseolus vulgaris L.) is the world’s most important food legume; it provides up to. Common bean can establish symbiosis with soil bacteria known as rhizobia to capture atmospheric N2 and thereby to support plant growth. The common bean crop is grown by smallholder farmers in Latin America and East Africa, where it is often exposed to unfavorable conditions and minimum use of inputs [1,2,3]. About 60% of common beans produced worldwide are grown in regions subjected to water stress, after diseases, drought is the second most important factor that contributes to yield reduction. The development of common bean varieties with improved water stress tolerance has been a long-time major objective for breeding programs in different regions [4,5]
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