Natural genetic variation studies in tomato (Solanum lycopersicum) for nitrogen uptake capacity

Author(s)

André Luiz Tagliaferro

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Centro de Energia Nuclear na Agricultura (CENA/STB)
• Defense date: 2015-09-04

Examining board members

Antonio Vargas de Oliveira Figueira; Leonardo Silva Boiteux; Victor Alexandre Vitorello

• Advisor: Antonio Vargas de Oliveira Figueira

Abstract

High nitrogen fertilizer input is required to increase the yield of tomato (Solanum lycopersicum) to attend to the rising world demand. N fertilization might result in a detrimental impact on the environment, such as contributing to greenhouse gases and groundwater pollution. One approach to reducing the excessive use of N fertilizers is the evaluation of natural genetic variability for N use efficiency (NUE) of crop plants. Therefore, the genotypes S. pimpinellifolium, S. lycopersicum cv \'Santa Clara\', and S. habrochaites, previously identified with contrasting capacity of N absorption, were used in kinetic and provision assays using short-term 15N-labeled. Furthermore, the relative quantification of gene expression via quantitative reverse transcription PCR (RT-qPCR) of genes related to the ammonium transport (AMTs - AMMONIUM TRANSPORTER - AMT1.1, AMT1.2 and AMT2.1) and nitrate (NRTs - NITRATE TRANSPORTERS - NRT1.1, NRT2.1, NRT2.2 and NAR2) was performed to correlate the N absorption capacity with the expression of these genes. Solanum pimpinellifolium has greater ammonium absorption in its roots when compared to genotypes S. lycopersicum cv \'Santa Clara\' and S. habrochaites under contrasting conditions of N availability. This phenotype is associated with the greater induction of SlAMT1.1 expression in S. pimpinellifolium roots. During ammonium provision, genotype S. habrochaites showed lower inhibition of the 15N-ammonium acquisition compared to S. lycopersicum cv \'Santa Clara\' and S. pimpinellifolium. The correlation with the expression levels of the main ammonium transporter suggests a different allosteric regulation of SlAMT1.1 protein in S. habrochaites. The comparison of the SlAMT1.1 coding region in the three genotypes indicated the existence of differences in amino acid sequence, particularly in S. habrochaites. The change of Ser240Gly in the cytosolic loop of S. habrochaites, which is critical during the allosteric regulation, may be related to the inhibition of ammonium influx. The cloning and sequencing of the promoter region of the gene SlAMT1.1 indicates the presence of different regulatory motifs in the promoter of SlAMT1.1 in S. pimpinellifolium when compared to S. lycopersicum cv Santa Clara and S. habrochaites. This can be correlated with the highest ammonium acquisition capacity of S pimpinellifolium roots. Therefore, nitrate kinetic studies showed that S. pimpinellifolium has greater acquisition of nitrate in their roots when compared to S. lycopersicum cv Santa Clara and S. habrochaites, due to increased induction of SlNRT2.1 and SlNRT2.2 genes. The correlation among nitrate influx studies and expression of genes related to the transport of this N form suggest that SlNRT2.1 is the main transporter regulated in roots of the three genotypes under nitrate supply. In addition, the genotype S. habrochaites showed greater ability to induce SlNRT2.1 when compared to S. lycopersicum cv \'Santa Clara\' and S. pimpinellifolium in nitrate supply (AU)

• FAPESP's process: 13/09551-0 - NATURAL GENETIC VARIATION STUDIES IN TOMATO (SOLANUM LYCOPERSICUM) FOR NITROGEN UPTAKE CAPACITY
• Grantee: André Luiz Tagliaferro
• Support Opportunities: Scholarships in Brazil - Master