A novel NAC transcription factor from Haloxylon ammodendron promotes reproductive growth in Arabidopsis thaliana under drought stress

Maintaining the growth of reproductive branches during the summer is crucial for the seed setting of the perennial xerophytic plant H. ammodendron (Haloxylon ammodendron). In this study, we screened and cloned the NAC transcription factor HaNAC12 from the transcriptomes of different tissue of the desert plant H. ammodendron and from the transcriptome of seedlings under drought stress. Real-time quantitative fluorescence analysis showed that the expression level of HaNAC12 in reproductive branches was higher than that in vegetative branches. It was able to respond to treatments of drought, high salinity and low-temperature stress, as well as to the external induction of plant hormones such as IAA, ABA, SA and MeJA. The GFP- HaNAC12 fusion protein localized to the nucleus of tobacco epidermal cells. Heterologous expression of HaNAC12 revealed that the transgenic Arabidopsis exhibited enhanced drought resistance and showed early flowering after natural drought stress, promoting reproductive growth. Transcriptomic analysis indicated that fatty acid metabolic pathways were upregulated in transgenic Arabidopsis thaliana. DNA affinity purification analysis showed that HANAC12 binds to elements in the downstream target genes primarily associated with the linoleic acid metabolic pathway. The total fatty acid content in the reproductive branches of transgenic Arabidopsis and H. ammodendron is greater than that in the wild-type Arabidopsis and the vegetative branches of H. ammodendron. Under drought stress, plants can adapt to arid conditions by increasing the proportion of unsaturated fatty acids, thereby enhancing membrane fluidity, reducing membrane damage, and maintaining the requirements for cell division and growth. Therefore, HaNAC12 may improve the drought resistance of Arabidopsis and promote reproductive growth under drought stress by regulating fatty acid metabolism.