SlCESTA Is a Brassinosteroid-Regulated bHLH Transcription Factor of Tomato That Promotes Chilling Tolerance and Fruit Growth When Over-Expressed

Abstract

Brassinosteroids (BRs) are required for various aspects of plant growth and development, but also participate in stress responses. The hormones convey their activity through transcriptional regulation and posttranslational modification of transcription factors and one class are basic helix-loop-helix (bHLH) proteins of the BR Enhanced Expression (BEE) subfamily, which in Arabidopsis thaliana include BEE1-3 and CESTA (CES). CES and the BEEs promote the expression of different BR-responsive genes, including genes encoding gibberellin (GA) biosynthetic and catabolizing enzymes, as well as cold-responsive genes. Interestingly, in terms of an application, CES could promote both fruit growth and cold stress tolerance when over-expressed in A. thaliana and here it was investigated, if this function is conserved in the fruit crop Solanum lycopersicum (cultivated tomato). Based on amino acid sequence similarity and the presence of regulatory motifs, a CES orthologue of S. lycopersicum, SlCES, was identified and the effects of its over-expression were analysed in tomato. This showed that SlCES, like AtCES, was re-localized to nuclear bodies in response to BR signaling activation and that it effected GA homeostasis, with related phenotypes, when over-expressed. In addition, over-expression lines showed an increased chilling tolerance and had altered fruit characteristics. The possibilities and potential limitations of a gain of SlCES function as a breeding strategy for tomato are discussed.

Functions of Basic Helix–Loop–Helix (bHLH) Proteins in the Regulation of Plant Responses to Cold, Drought, Salt, and Iron Deficiency: A Comprehensive Review

“…SlbHLH96 physically interacts with an ETHYLENE-RESPONSIVE FACTOR (SlERF4). This binary complex interferes the expression of the ABA catabolic gene (SlCYP707A2) through binding to its promoter. , The bHLH transcription factor TaAKS1 and TaERF87 form heterodimers to synergistically mediate proline biosynthesis through activation the expression of the Δ-1-PYRROLINE-5-CARBOXYLATE SYNTHETASE (TaP5CS1) and Δ-1-PYRROLINE-5-CARBOXYLATE REDUCTASE (TaP5CR1), resulting in enhancement of drought tolerance …”

Genome-Wide Identification and Characterization of the bHLH Gene Family and Its Response to Abiotic Stresses in Carthamus tinctorius

“…They deftly choreograph embryo development [14], harmonize the formation of reproductive organs [15], and regulate both fruit and seed developmental processes [16]. Moreover, their influence extends to anthocyanin synthesis [6], light signaling [17], and brassinosteroid cascades [18]. Thus, the bHLH TFs interweave the intricate threads of both developmental intricacies and adaptive prowess, establishing connections that intertwine core regulatory pathways with stress-responsive mechanisms in plants.…”