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. 2023 Mar 9;24(6):5253. doi: 10.3390/ijms24065253

Figure 1.

Figure 1

(HY5), UV resistance locus 8 (UVR8), phototropins (PHOTs), phytochromes (PHYs) and cryptochromes (CRYs) are regarded as photoreceptors with a response to light, and they act as the upstream of auxin-signaling-related genes or proteins. PHOTs could interact with PHYTOCHROME KINASE SUBSTRATE 1 (PKS1), ROOT PHOTOTROPISM 2 (RPT2) and NON-PHOTOTROPIC HYPOCOTYL 3 (NPH3), and act as the upstream of the auxin-signaling-related genes PINs. The MYB domain protein 73/77 (MYB73/MYB77) acts as the downstream of UVR8 to regulate auxin responses and lateral root growth. In the auxin-signaling transduction pathway, PIN-formed (PINs), YUCs, auxin response factors (ARFs) and LIKE AUX3 (LAX3) are key genes, and act as the downstream of light-response-related genes or proteins. When a plant is exposed to light, miR775 could induce the root growth and development by regulating root-hair-related genes such as ROOTHAIR DEFECTIVE SIX-LIKE (RSLs) and PROTEIN PHOSPHATASE 2A (PP2A). MEDIATOR18 (MED18) could promote root growth with continuous light via directly regulating auxin-signaling transduction-related genes. Moreover, MED18 triggered the transcript level of HY5, which led to chlorophyll accumulation. When a plant is exposed to light, HY1 induces the up-regulation of HY5 and HYH, then HY5 triggers the expression of auxin-signaling-related genes IAAs, which finally promotes root branching. Furthermore, HY1 can directly regulate root branching via enhancing the transcript level of PINs and AUX1. The arrows mean that one protein or stimuli could directly and positively act as the upstream to regulate another protein. The double arrows represent interactions between proteins. The “T” shape indicates that one stimuli could negatively regulate the protein.