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Acta Prataculturae Sinica ›› 2023, Vol. 32 ›› Issue (1): 178-191.

### Cloning and identification of drought tolerance function of the LjbHLH34 gene in Lotus japonicus

Fu LIU1,2(), Cheng CHEN1,2, Kai-xuan ZHANG2, Mei-liang ZHOU2(), Xin-quan ZHANG1()

1. 1.College of Grassland Science and Technology，Sichuan Agricultural University，Chengdu 611130，China
2.Institute of Crop Sciences，Chinese Academy of Agricultural Sciences，Beijing 100081，China
• Received:2022-01-06 Revised:2022-02-24 Online:2023-01-20 Published:2022-11-07
• Contact: Mei-liang ZHOU,Xin-quan ZHANG

Abstract:

Drought is an important environmental factor affecting plant growth and development. In this paper， we studied the drought tolerance function of the gene LjbHLH34， and conducted a preliminary analysis of its molecular mechanism in response to drought stress， in order to provide a theoretical basis for molecular breeding of Lotus japonicus drought resistance. In this study， the size of LjbHLH34 was found to be 711 bp and to encode 236 amino acids， belonging to the bHLH transcription factor family. Phylogenetic tree analysis showed that LjbHLH34 was closely related to AtbHLH34 and AtbHLH104 in the bHLH Ⅳ subfamily of Arabidopsis thaliana. The expression level of LjbHLH34 was the highest in the roots， the second highest in the leaves， and the lowest in the stems， suggesting that LjbHLH34 plays a role in multiple tissues of L. japonicus.LjbHLH34 gene expression was also induced by polyethylene glycol （PEG） and abscisic acid （ABA）. A yeast assay showed that LjbHLH34 had transcriptional activation activity， and a subcellular localization assay showed that LjbHLH34 was located in the nucleus. Under 200 mmol·L-1 D-Mannitol stress， the root length of LjbHLH34 transgenic A. thaliana was significantly longer than that of the wild type. After drought treatment， the degree of withering of the wild-type was more obvious than transgenic Arabidopsis. At the same time， the relative water content and superoxide dismutase （SOD） activity of transgenic Arabidopsis were significantly higher than those of the wild-type， while malondialdehyde （MDA） accumulation was significantly lower than in the wild-type. qRT-PCR showed that the expression levels of stress-related genes AtCAT1AtCAT3 and AtRD22 in transgenic lines were significantly increased after drought treatment. These results indicated that LjbHLH34 positively regulates drought resistance of plants.