Recently, Journal of integrated plant biology (jipb) online published a research review entitled "b-box proteins: pivotal players in light mediated development in plants" written by Professor Xu Dongqing's Laboratory of Agricultural College of Nanjing Agricultural University. Summarize the b-box Bbxs family proteins play an important role in the growth and development of plants mediated by light signals. The latest research of bbxs proteins in model plants, Arabidopsis, different crops, including rice and soybean, and many horticultural crops, such as chrysanthemum, pear and apple trees, in the regulation of photoperiod flowering, photomorphogenesis and photoinduced pigment accumulation and synthesis is summarized Progress has been made.
BBX protein has at least one conserved b-box domain at the N-terminal and sometimes a CCT (CONSTANS, CO like and TOC1) domain at the C-terminal. According to the protein domain, it can be divided into five subfamilies. The b-box motif consists of about 40 residues, c-x2-c-x7-9-c-x2-d-x4-c-x2-c-x3-4-h-x4-8-h, where X represents any amino acid. The integrity of b-box domain is very important for the regulation of various cell and physiological functions, including the formation of nuclear spots, protein-protein interaction, and direct binding with DNA.
The first b-box family protein member identified and cloned in Arabidopsis thaliana is Co / bbx1, which contains two b-box domains at N-terminus and one CCT domain at C-terminus. CO is the key factor to induce long day flowering. It directly binds to the promoter region of FT through CCT domain to activate its transcription and initiate flowering. Co-ft regulation mode is the key to control photoperiod flowering, and it is highly conserved in many plants. In addition to CO, multiple BBX, such as bbx4 / col3, bbx5 / col4, bbx6 / col5, bbx7 / col9, bbx10 / col12, bbx19, bbx24, bbx30 / mip1a, bbx31 / mip1b and bbx32, can mediate flowering through different molecular mechanisms. Bbxs are conserved in different species. For example, there are 30 BBX members in rice, many of which are also involved in the regulation of flowering pathway. The mechanism of bbxs is different and redundant in the regulation of flowering. In conclusion, BBX protein may be able to control flowering sensitively by forming a precise regulatory network in response to seasonal changes of light signals.
Light signals closely regulate the occurrence of photomorphogenesis and dark morphogenesis of plant seedlings. In these two different developmental processes, many biological factors, including photoreceptors, E3 ubiquitin ligases and transcription regulators, work together to respond to changes in light signals. Systematic studies have shown that bbxs, as transcription factors or transcriptional regulators, play a variety of roles in the regulation of light signals in seedling development. Bbx4 specifically mediates the growth of seedlings regulated by red light. Bbx20 / bzs1, bbx21, bbx22 and bbx23 positively regulated light morphogenesis, while bbx19, bbx24, bbx25, bbx28, bbx30, bbx31 and bbx32 negatively regulated light morphogenesis. At the same time, the expression of bbxs is dynamically regulated by light signals and acts on the downstream of various photoreceptors, regulating the transcription of many light response genes. At the same time, bbxs can interact with other transcription factors (such as HY5 and PIFS) to form a complex and fine regulatory network, and accurately control a large number of downstream gene transcription, so as to accurately regulate plant photomorphogenesis. The function of b-box domain is different in these regulatory roles, and the different motifs or regions on a single BBX protein may have unique or common molecular functions, and the changes of these regions may lead to the diversity of their biological functions.
Bbxs regulate plant photomorphogenesis.
The identification and functional exploration of bbxs provide new insights for understanding the light regulation of plant growth and development. The summary of the research progress of bbxs in the development pathway mediated by light signals in recent years will help people to have a further understanding of the biological functions of bbxs, and help people to put forward effective strategies for improving agricultural properties of crops according to the growth and development pathway of plants mediated by bbxs. The corresponding author of this review is Professor Xu Dongqing of Nanjing Agricultural University, the first author is song Zhaoqing, a doctoral student of Nanjing Agricultural University, and the author is Bian Yiting, a postgraduate student, Liu Jiujie and sun Yuting, an undergraduate student.
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