Identification and functional analysis of signal transduction-related genes in sugarcane.

Author(s)

Flávia Riso Rocha

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2006-08-09

Examining board members

Glaucia Mendes Souza; Dirce Maria Carraro; Paulo Lee Ho; Eduardo Moraes Rego Reis; Michel Georges Albert Vincentz

• Advisor: Glaucia Mendes Souza

Abstract

A diversity of processes related to growth, development and adaptation to environmental conditions are regulated by signal transduction pathways. The SUCAST Project (Sugarcane Signal Transduction) (Souza et al., 2001) aims to identify, characterize and associate putative functions to sugarcane signal transduction components using bioinformatic tools and to evaluate their expression profiles using cDNA microarrays. BLAST searches conducted on sequences stored in the SUCEST databank - The Sugar Cane EST Project (Vettore et al., 2003) - revealed more than 3,500 putative genes related to signaling in sugarcane. The protein kinases were anaçyzed for the presence of conserved domains and classified according to a phylogenetic analysis of the predicted catalytic domain. The phylogenetic approach indicated six characteristic groups for protein kinases and four mains groups for receptor-like kinases. The expression patterns of SUCAST components were evaluated in six organs (root, flower, leaf, lateral bud, first and fourth internodes), in response to different stimuli (treatment with the phytohormones abscisic acid and methyljasmonate, drought, endophytic bacteria interaction, attack by Diatraea saccharalis and phosphate deficiency) and in sugarcane cultivars contrasting for sucrose accumulation. The tissue profiling experimenta showed 217 differentially expressed genes in at least one of the six organs analyzed and 153 genes of ubiquitous expression. A total of 179 differentially expressed genes were obtained in response to phytohormones and environmental stimuli, in at least one of the conditions analyzed were obtained. Comparisons between high and low sucrose (brix) cultivars led to the detection of 51 differentially expressed genes in at least one of the samples analyzed (leaves +1 and internodes at different maturing stages). The expression patterns were also analyzed in time-course experiments of phosphate deficiency, drought and phytohormone treatments by Self-Organizing Maps (SOM) clusterization. Quantitative PCR results confirmed 72% of the microarray expression data in sugarcane organs for 25 selected genes and 80.5% of the 36 expression profiles selected in response to phytohormones and environmental stimuli. Additionally, real-time PCR reactions were carried out to evaluate the expression levels of five genes in individuals contrasting for sucrose accumulation and 57% of the results obtained were in agreement with the microarray data. All data generated were integrated and compiled into the SUCAST databank (http://www.sucest-fun.org). The knowledge generated adds to the comprehension of the function of SUCAST components, indicating targets to be explored in the improvement of sugarcane cultivars. (AU)