**1. Pigment Formation**

Orchid populations have always been good materials for revealing the secrets of plant evolution. Zhang et al. studied species evolution using comparative transcriptomics in the *P. limprichtii* population that has a wide range of floral color varieties [1]. They proposed that the distribution pattern of different color morphs may be considered as a reproductive strategy that plays an important role in maintaining the population size. In this study, a molecular mechanism of color variation was proposed in which a crucial gene *PlFLS* interacts with a putative MBW protein complex (MYB, bHLH, and WDR), which may sever as a repressor of anthocyanin accumulation.

Flower spot patterning could affect the ornamental value of some orchids and may play a significant role in the interaction with pollinators. Zhao et al. used a transcriptome analysis in the anthocyanin biosynthetic pathways of *Phalaenopsis* "Panda" to identify differentially expressed genes (DEGs) [2]. They further confirmed that some candidate structure genes among the DEGs expressed in significantly higher levels in spot tissues using qPCR analysis. Eventually, differentially expressed miRNAs (DEMs) were analyzed and 40 DEMs target transcription factor genes were found to express in significantly different levels in the spot sepal. According to the results, they proposed a microRNA-suppressing model for explaining the regulation in flower spot formation.

A comparative metabolomic study was made by Gao et al. and aims to reveal the regulation of flavonoid biosynthesis that contribute to leaf color formation in a foliage orchid, *Cymbidium sinense* "Red Sun" [3]. They identified 196 flavonoid-related metabolites using a UPLC-MS/MS-based method and revealed that the trends of leaf color changing from red to yellow and eventually to green, were mainly contributed by down-regulated anthocyanin biosynthetic enzymes.
