Expression patterns of three α‐expansin isoforms in Coffea arabica during fruit development

Abstract

As a first step towards understanding the physiological role and regulation of the expansin gene (EXP) family in Coffea arabica fruits during growth and maturation, we identified 11 expansin genes, nine belonging to the α-expansin family (EXPA), one EXLA and one EXLB, through in silico analysis of expressed sequence tags (ESTs). Within the α-expansin family, three isoforms were selected for detailed examination based on their high expression in coffee fruits or because they were specifically induced during different fruit developmental stages, according to the EST information. The expression patterns were analysed in different fruit tissues (perisperm, endosperm and pericarp) of C. arabica cv. IAPAR-59 and C. arabica cv. IAPAR-59 Graúdo, the latter being a closely related cultivar with a larger fruit size. Accumulation of CaEXPA1 and CaEXPA3 transcripts was high in the perisperm (tissue responsible for coffee bean size) and in the early stages of pericarp development. Transcripts of CaEXPA2 were detected only in the pericarp during the later stages of fruit maturation and ripening. There was no detectable transcription of the three EXPs analysed in the endosperm. The observed differences in mRNA expression levels of CaEXPA1 and CaEXP3 in the perisperm of IAPAR-59 and IAPAR-59 Graúdo suggest the participation of these two isoforms in the regulation of grain size.

Identification of expressed sequences in the coffee genome potentially associated with somatic embryogenesis

“…Expansins promote the relaxation of the cellular wall at the onset of ripening of various fruit species (Harrison et al, 2001). In C. arabica, 2 expansin genes (CaEXPA1 and CaEXP3) are directly related to the size of the fruit (Budzinski et al, 2011). In L. esculentum, however, expansin genes (LeEXP4, LeEXP8, and LeEXP10) are involved in embryonic development and germination (Chen and Bradford, 2000).…”

“…Therefore, considering that contig 17265 was expressed approximately 57 times higher in silico in the EC1 than in the fruit library, it may be more involved in coffee plant embryogenesis than in the increase of fruit size, as described in C. canephora (Budzinski et al, 2011). Although the EST-contigs analyzed indicate involvement in the somatic embryogenesis of the coffee plant, functional genomics analyses are necessary to evaluate whether these genes can be used as markers of embryogenic acquisition processes in coffee.…”

Gene expression and enzymatic activity of pectin methylesterase during fruit development and ripening in Coffea arabica L.

“…In silico identification of C. arabica putative PME unigenes followed similar steps as those described in Budzinski et al (2011). ESTs coding for PME were selected from the database of the Brazilian Coffee Genome Project (http://www.lge.ibi.unicamp.br/cafe) using a key word search.…”

“…IAPAR-59 plants cultivated under field conditions at the Agronomic Institute of Paraná Experimental Station (Londrina, Brazil) from December 2006 to April 2007. Fruits were collected every 90 days after flowering until complete maturation and were separated by perisperm color as previously described (Budzinski et al, 2011). Unless otherwise stated, experiments were conducted at least twice with a minimum of 3 biological replicates per experiment.…”

Functional identification of anEXPAgene (NcEXPA8) isolated from the treeNeolamarckia cadamba

“…In A. thaliana, AtEXPA2, which is exclusively expressed in germinating seeds [19], controls seed germination [20]. In Coffea arabica fruits, CaEXPA1 and CaEXP3 regulate grain size during growth and maturation [21,22]. Expansins are also involved in the stress response [23][24][25]; however, little is known about the mechanism by which expansins operate in plants during the adaptive responses to adverse stresses.…”