Characterization of 10 MADS-box genes from Pyrus pyrifolia and their differential expression during fruit development and ripening.

We cloned 10 Japanese pear (Pyrus pyrifolia) MIKC-type II MADS-box genes, and analyzed their expression during fruit development and ripening. PpMADS2-1 was APETALA (AP)1-like; PpMADS3-1 was FRUITFULL (FUL)/SQUAMOSA (SQUA)-like; PpMADS4-1 was AGAMOUS-like (AGL)6; PpMADS5-1 and PpMADS8-1 were SUPPRESSOR OF OVEREXPRESSION OF CONSTANS (SOC)-like; PpMADS9-1, PpMADS12-1, PpMADS14-1 and PpMADS16-1 were SEPALLATA (SEP)-like; while PpMADS15-1 was AGL/SHATTERPROOF (SHP)-like. Phylogenetic analysis showed their grouping into five major clades (and 10 sub-clades) that was consistent with their diverse functional types. Expression analysis in flower tissue revealed their distinct putative homeotic functional classes: A-class (PpMADS2-1, PpMADS3-1, PpMADS4-1, and PpMADS14-1), C-class (PpMADS15-1), E-class (PpMADS9-1, PpMADS12-1, and PpMADS16-1) and E (F)-class (PpMADS5-1 and PpMADS8-1). Differential gene expression was observed in different fruit tissues (skin, cortex and core) as well as in the cortex during the course of fruit development and ripening. Collectively, our results suggest their involvement in the diverse aspects of plant development including flower development and the course of fruit development and ripening.