Functional Analysis of the Genotypic Differences in Response of Pea (Pisum sativum L.) to Calcareous-Induced Iron Deficiency

Lime-induced iron chlorosis is a major nutritional disorder causing severe plant growth and yield reduction in the calcareous soils of Tunisia.The understanding the behavior of key metabolic functions of peas on calcareous soils,the identification of useful traits of tolerance,and the exploration of the genotypic differences in response to this constraint remain the most efficient approaches due to their coast,environmental benefits,and sustainability.For this purpose,a greenhouse experiment was conducted on three pea genotypes(Alexandra:Alex,Douce de provence:DP,and Merveille de Kelvedon:MK)cultivated on calcareous soil(Fe-deficient)and fertile soil(control).Plant growth,SPAD index,iron nutrition and distribution,photosynthesis,and antioxidant enzymes were deeply analyzed to discriminate genotypic differences.Calcareous-induced iron deficiency reduced SPAD index,plant growth,net photosynthesis,and tissue Fe content against a significant stimulation of the oxidative stress indicators,H2O2 and Malondialdehyde(MDA).Moreover,we reported a significant induction of SOD and CAT activity in shoots and roots of the Alexandra genotype.Fe use efficiency increased on calcareous soil and clearly discriminated the studied genotypes.Alexandra genotype was found to be the most tolerant to lime-induced iron chlorosis.This genotype protects its tissues against oxidative stress by stimulating enzyme activities(SOD and CAT)and develops significant efficiency of Fe uptake,translocation to shoots and use when cultivated on calcareous soil.

Comparative Transcriptomic Analysis of Salt Adaptation in Roots of Contrasting Medicago truncatula Genotypes

Evolutionary diversity can be driven by the interaction of plants with different environments. Molecular bases involved in ecological adaptations to abiotic constraints can be explored using genomic tools. Legumes are major crops worldwide and soil salinity is a main stress affecting yield in these plants. We analyzed in the Medicago truncatula legume the root transcriptome of two genotypes having contrasting responses to salt stress： TN1.11, sampled in a salty Tunisian soil, and the reference Jemalong A17 genotype. TN1.11 plants show increased root growth under salt stress as well as a differential accumulation of sodium ions when compared to A17. Transcriptomic analysis revealed specific gene clusters preferentially regulated by salt in root apices of TN1.11, notably those related to the auxin pathway and to changes in histone variant isoforms. Many genes encoding transcription factors （TFs） were also differentially regulated between the two genotypes in response to salt. Among those selected for functional studies, overexpression in roots of the A17 ge- notype of the bHLH-type TF most differentially regulated between genotypes improved significantly root growth under salt stress. Despite the global complexity of the differential transcriptional responses, we propose that an increase in this bHLH TF expression may be linked to the adaptation of M. truncatula to saline soil environments.