H. Nair

‘Movers and shakers’ in the regulation of fruit ripening: a cross-dissection of climacteric versus non-climacteric fruit

Fruit ripening is a complex and highly coordinated developmental process involving the expression of many ripening-related genes under the control of a network of signalling pathways. The hormonal control of climacteric fruit ripening, especially ethylene perception and signalling transduction in tomato has been well characterized. Additionally, great strides have been made in understanding some of the major regulatory switches (transcription factors such as RIPENING-INHIBITOR and other transcriptional regulators such as COLOURLESS NON-RIPENING, TOMATO AGAMOUS-LIKE1 and ETHYLENE RESPONSE FACTORs), that are involved in tomato fruit ripening. In contrast, the regulatory network related to non-climacteric fruit ripening remains poorly understood. However, some of the most recent breakthrough research data have provided several lines of evidences for abscisic acid- and sucrose-mediated ripening of strawberry, a non-climacteric fruit model. In this review, we discuss the most recent research findings concerning the hormonal regulation of fleshy fruit ripening and their cross-talk and the future challenges taking tomato as a climacteric fruit model and strawberry as a non-climacteric fruit model. We also highlight the possible contribution of epigenetic changes including the role of plant microRNAs, which is opening new avenues and great possibilities in the fields of fruit-ripening research and postharvest biology.

Isolation and Characterization of Senescence-Associated Ethylene Genes from Dendrobium Orchids

Pollination hastens senescence in most flowers via the regulation of the ethylene pathway. This phenomenon impacts on the lucrative orchid cut flower industry when attractive hybrids that are ethylenesensitive undergo rapid post-pollination induced senescence. Manipulation of ethylene-associated genes could overcome the problem in transgenic orchids if ethylene biosynthesis is suppressed or if the signal transduction pathway is confounded. While ACCO oxidase and ACC synthase have been acknowledged as key enzymes in the ethylene biosynthesis pathway, knowledge about ethylene receptors in orchids is still quite limited and often confusing. In our studies with Dendrobium Pompadour orchids, we have isolated the genes for ACC oxidase and ACC synthase as well as those for two ethylene receptors first characterized in Arabidopsis, namely ETR1and ERS1. Physiological studies have shown that within 24 h, pollinated Dendrobium flowers display an increase in ethylene production after Zuliana Razali , S. Chandran , Lee Ai Ling , A.N. Boyce , 327 Z. Xu et al. (eds.), Biotechnology and Sustainable Agriculture 2006 and Beyond, 327–332.