Beyond Arabidopsis: BBX Regulators in Crop Plants

Abstract

B-box proteins represent diverse zinc finger transcription factors and regulators forming large families in various plants. A unique domain structure defines them—besides the highly conserved B-box domains, some B-box (BBX) proteins also possess CCT domain and VP motif. Based on the presence of these specific domains, they are mostly classified into five structural groups. The particular members widely differ in structure and fulfill distinct functions in regulating plant growth and development, including seedling photomorphogenesis, the anthocyanins biosynthesis, photoperiodic regulation of flowering, and hormonal pathways. Several BBX proteins are additionally involved in biotic and abiotic stress response. Overexpression of some BBX genes stimulates various stress-related genes and enhanced tolerance to different stresses. Moreover, there is evidence of interplay between B-box and the circadian clock mechanism. This review highlights the role of BBX proteins as a part of a broad regulatory network in crop plants, considering their participation in development, physiology, defense, and environmental constraints. A description is also provided of how various BBX regulators involved in stress tolerance were applied in genetic engineering to obtain stress tolerance in transgenic crops.

Genome-Wide Identification, Evolution, and Comparative Analysis of B-Box Genes in Brassica rapa, B. oleracea, and B. napus and Their Expression Profiling in B. rapa in Response to Multiple Hormones and Abiotic Stresses

“… Scheme illustrating major features of BBX proteins in each structure group (Modified from Talar et al [ 11 ]). …”

“…In tomato, rice, apple, and grapevine, some stress-and hormone signaling-related cis-elements, such as the LTR, MBS, HSE, ABA-responsive element (ABRE), ethylene-responsive element (ERE), and gibberellin-responsive element (GARE), have been detected in the promoter region of most BBX genes, implying these genes are involved in hormone signaling pathways and abiotic stress responses [8,[31][32][33] Figure 1. Scheme illustrating major features of BBX proteins in each structure group (Modified from Talar et al [11]).…”

An Evolutionary Analysis of B-Box Transcription Factors in Strawberry Reveals the Role of FaBBx28c1 in the Regulation of Flowering Time

“…However, the biological significance of these family expansion events for the flowering regulation mechanism of strawberry need to be further explored, since functional studies of the above genes in plant flowering regulation remain scarce. BBX genes are reported to play diverse functional roles in plant biological processes [4]. Increasing evidence has demonstrated that BBXs show special gene expression patterns related to their function.…”

“…Numerous analyses concerning the biological functions of AtBBXs have been reported. The biological functions of AtBBXs are associated with multiple physiological and biochemical processes, including developmental regulation, flowering time regulation, and response to external stress [2,4]. AtBBX28 is a negative regulator of AtHY5 that participates in the COP1-HY5 pathway mediating photomorphogenic development via a physical interaction with the AtHY5 protein, which represses the activity of AtHY5 in a dose-dependent manner in Arabidopsis [5].…”

CpBBX19, a B-Box Transcription Factor Gene of Chimonanthus praecox, Improves Salt and Drought Tolerance in Arabidopsis

“…The BBX gene family, encoding zinc-finger proteins, is an important family of transcription factors in plants, with functions including response to environmental changes, and plant growth and development [ 13 , 14 ]. BBX proteins generally have one or two B-box domains, and some members also have VP domains and CCT domains [ 15 ]. In plants, the B-box domain contains approximately 40 amino acids and is highly conserved, but there are still some differences among different B-box motifs [ 16 , 17 ].…”