## 1 Introduction  
Plant secondary metabolites are often produced either in certain tissues or cells under stress conditions or induced by various developmental, hormonal and environmental cues. The biosynthesis of secondary metabolites is often tightly regulated at transcriptional levels. Even in a plant cell where secondary metabolites are synthesized, the multiple enzymes and their reactions are often compartmentalized into various subcellular organelles, such as chloroplast, endoplasmic reticulum (ER), vacuoles, as well as apoplastic spaces. It is also often observed that the synthetic site of secondary metabolites is usually different from the site where these chemicals function, as defensive compounds against insects, bacteria or fungal pathogens. Thus, efficient transport of precursors, metabolic intermediates and the end products for biosynthesis, storage or function, are of critical in whole plant secondary metabolism and their biological significance. Many studies support the idea that transporters, either across membranes or intra-cellular trafficking, or inter-cellular long distance transport, provide another layer of regulation for metabolic flux [1; 2]. Furthermore, these transmembrane transporters, vesicle trafficking components, as well as protein carriers are also regulated at transcriptional levels [3]. Therefore, transcriptional and transport regulation of secondary metabolite biosynthesis are critical research topics.  
_Catharanthus roseus_ (Madagascar periwrinkle) is a perennial herb belonging to the family Apocynaceae. It produces over 100 different terpenoid indole alkaloids (TIAs), some of which exhibit strong pharmacological activities and are essentially used in clinical treatment of various diseases [4]. Vinblastine and vincristine, which have been used clinically to treat cancers since 1950s, are the most valuable dimeric TIAs in _C. roseus_[5]. These two dimeric TIAs are produced in trace amount in _C. roseus_ by coupling vindoline and catharanthine, both of which have also been reported with anti-bacterial activities, anti-diabetic properties and diuretic actions [6]. Other TIAs from _C. roseus_ such as ajmalicine and serpentine are used in anti-hypertensive and anti-neuro-inflammatory agents [6]. Due to extremely low yield of the highly valuable vinblastine and vincristine, substantial efforts in past decades have put on large-scale cell culture, bioreactor processing biotechnology and metabolic engineering to improve their production in order to meet the increasing demands from the market. However, the success is very limited. It has been realized that understanding of the TIA biosynthesis, transport and their regulation may empower our ability to apply new and robust molecular and genetic tools in metabolic engineering of the production of these valuable metabolites [7; 8; 9; 10]. Several reviews were published about the organ-, tissue- and cell-specific as well as transcriptional regulation of TIA biosynthesis [8; 11]. However, the breakthroughs made recently on TIA biosynthesis regulation and particularly, the intra- and inter-cellular TIA transport, from molecular biology, genomic and transcriptomics points of view have provided significant insights into these important dynamic cellular processes [12]. This review is to summarize these most recent progresses made on TIA biosynthesis, transcriptional regulation and their transport and to employ transcriptome analysis for further looking for TIA transcriptional regulators that are potentially involved in the TIA biosynthesis.