Genome-wide identification of jasmonate biosynthetic genes and their characterization of their expression profiles during apple (Malus x domestica) fruit maturation

Authors: LV, JINGYI - Northwest Agriculture And Forestry University; RAO, JINGPING - Northwest Agriculture And Forestry University; JOHNSON, FRANKLIN - Washington State University; Shin, Sung; Zhu, Yanmin

Submitted to: Plant Growth Regulation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2014
Publication Date: 1/15/2015
Citation: Lv, J., Rao, J., Johnson, F., Shin, S.B., Zhu, Y. 2015. Genome-wide identification of jasmonate biosynthetic genes and their characterization of their expression profiles during apple (Malus x domestica) fruit maturation. Plant Growth Regulation. 73:335-364.

Interpretive Summary: The plant hormones regulate most physiological processes including fruit ripening. Multiple plant hormones function at the upper stream of apple fruit ripening process by integrating both developmental cues and environmental signals. Furthermore, plant hormones rarely work individually, instead that their crosstalk results in either antagonistic or synergistic interaction. Ethylene has been extensively studied for its role regulating apple fruit maturation and ripening, recent functional genomics studies suggest jasmonic acid (JA) and its derivatives, as well as the interplay between JA and ethylene, are also critical in regulating apple fruit ripening. Up till now, the JA’s role in apple fruit ripening has been primarily associated with exogenous application and its demonstrated alternations in apple fruit ripening phenotypes. On the other hand, the endogenous JA biosynthesis and signal transduction in apple fruit tissues has not been examined. In this study, the members of major gene families in JA biosynthesis pathway were identified from apple genome sequences; and their expression profiles were characterized using quantitative reverse transcription PCR (qRT-PCR). Our data demonstrated the up-regulated expression patterns at the late stages of maturation of apple fruit for MdLOX23, MdAOS2 and MdJMT2 of JA biosynthesis pathway, which are coordinated with the expression patterns of genes in ethylene signaling pathway, i.e. MdACS3, MdERF1 and MdERF2. These observations are the first experimental data regarding the specific genes of innate JA biosynthesis pathway in apple fruit. Our result also suggested the crosstalk between ethylene and JA pathways. The observed consistent expression patterns of MdLOX23 and MdAOS2 in both core and cortex tissues of apple fruit suggest the localized biosynthesis of JA in different fruit tissues, instead of JA transport from developing seeds. Most of JA biosynthesis genes were transiently up-regulated in response to exogenous application of methyl jasmonate (MeJA) to on-tree maturing apple fruit, but such stimulation is maturity-dependent.

Technical Abstract: The plant hormones regulate many physiological processes including apple fruit ripening by integrating diverse developmental cues and environmental signals. In addition to the well-characterized role of ethylene, jasmonic acid (JA) and its derivatives have also been suggested to play an important role during apple fruit maturation and ripening. Up till now, the JA’s role in apple fruit ripening has been primarily observed through exogenous application and the alternated apple fruit ripening processes. The endogenous JA biosynthesis and signal transduction in apple fruit tissues has not been studied. In this study, the members of major gene families in JA biosynthesis pathway were identified from apple genome sequences; and their expression profiles were characterized using quantitative reverse transcription PCR (qRT-PCR). Our data indicated that the up-regulated expression patterns for MdLOX23, MdAOS2 and MdJMT2 in JA biosynthesis pathway, particularly at the late stages of maturation. The expression of these genes showed the coordinated patterns with those of MdACS3, MdERF1 and MdERF2 genes in ethylene biosynthesis and signal transduction pathways. Both MdLOX23 and MdAOS2 demonstrated the comparable expression patterns in both core and cortex tissues suggesting the localized synthesis of JA in different fruit tissues. Most of JA biosynthesis genes were transiently up-regulated in response to exogenous application of methyl jasmonate (MeJA) to on-tree maturing apple fruit, though in a maturity-dependent manner. Our results suggested that JA biosynthesis and signaling regulate apple fruit maturation and ripening likely through the crosstalk with ethylene.