RIPENING-RELATED cDNAs IN GUAVA FRUIT (Psidium guajava L.). CHARACTERIZATION AND EXPRESSION ANALYSIS

Abstract

Bioinformatics analysis and gene expression studies of four clones of guava cDNA encoding for a polygalacturonase (PG), an acid 1-aminocyclopropane-1-carboxylate oxidase (ACCo), and two α-expansins (α-Exp) in guava (Psidium guajava L.), is presented here. Using RT-PCR, a partial cDNA fragment of 301 bp (PgPG1) was associated to a PG from mature fruit, one of 320 bp (PgACO1) for an ACCo in overriped fruit, and two fragments for α-expansins: a 466 bp (PgEXP2) of overripe fruit and a 362 bp of peduncle (PgEXP3). cDNA analysis showed that these fragments encode putative proteins with high homology with related proteins. The aminoacid sequence of PgPG1 contains particular features and conserved regions of the PGs in higher plants and is related to fruit ripening; PgACO1 showed features present in all the ACCo and is related to fruit maturation; PgEXP2 and PgEXP3 partially contain two domains present in expansins; and they are phylogenetically grouped with α-expansins. Dot Blot expression studies showed that gene PgPG1 was visible in all stages of fruit ripening, with higher intensity during mature stage. Gene PgACO1 was visible in the five stages of fruit ripening, and was highest during the transition stage (these two genes displayed behaviors similar to those reported in climacteric fruits); PgEXP2 gene expression was detected in all tissues, with an increase from the Green Stage 2 to Overripe Stage 1, as it has been reported in non-climacteric fruits; for PgEXP3 the expression was visible in four stages of fruit ripening and at peduncle, with highest intensity at the mature stage.