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In fleshy fruits, organic acids are the main source of fruit acidity and play an important role in regulating osmotic pressure, pH homeostasis, stress resistance, and fruit quality. The transport of organic acids from the cytosol to the vacuole and their storage are complex processes. A large number of transporters carry organic acids from the cytosol to the vacuole with the assistance of various proton pumps and enzymes. However, much remains to be explored regarding the vacuolar transport mechanism of organic acids as well as the substances involved and their association. In this review, recent advances in the vacuolar transport mechanism of organic acids in plants are summarized from the perspectives of transporters, channels, proton pumps, and upstream regulators to better understand the complex regulatory networks involved in fruit acid formation. [ABSTRACT FROM AUTHOR]

Basic helix−loop−helix (bHLH) domain-containing transcription factors are known for their roles in regulating various plant growth and developmental processes. Previously, we showed that MdbHLH3 from apple (Malus domestica) has multiple functions, modulating both anthocyanin biosynthesis and cell acidification. Here, we show that MdbHLH3 also regulates ethylene biosynthesis and leaf senescence by promoting the expression of dehydratase-enolase-phosphatase complex 1 (MdDEP1). Therefore, we propose a model whereby MdbHLH3 acts as a crucial factor that modulates anthocyanin biosynthesis and cell acidification in addition to fruit ripening and leaf senescence by regulating distinct target genes. [ABSTRACT FROM AUTHOR]

Lateral root (LR) formation and development play a vital role in plant development by permitting the establishment of branched root systems. It is well known that nutrient availability controls LR development. Moreover, LR development is fine-tuned by a myriad of hormonal signals. Many transcription factors (TFs) participate in LR development. Here, we discuss the TFs involved in the nitrate and auxin signaling pathways and how these function in the regulation of LR formation and development in chrysanthemum. AtTCP20 is a plant-specific TF, which can modulate LR development in response to nitrate. The roles of CmTCP20 in LR development were identified by overexpression in chrysanthemum and heterologous expression in Arabidopsis. Overexpression of CmTCP20 significantly increased the number and average length of LRs compared with the wild type in chrysanthemum and Arabidopsis. We also found that CmTCP20 positively influenced auxin accumulation in the LRs at least partly by improving auxin biosynthesis, transport and response, thereby promoting LR development. Moreover, we found that CmTCP20 interacts with an auxin response factor, CmARF8, which also can be induced by nitrate and combined to proximal sites in the upstream promoter region of CmCYCB1;1 to positively regulate the cell cycle. The CmTCP20-CmARF8 heterodimer links nitrate and auxin signaling and converts cell-cycle signals to regulate LR initiation and growth. [ABSTRACT FROM AUTHOR]