Cloning and functional analysis of the HaNAC11 transcription factor in Haloxylon ammodendron

The perennial desert plant Haloxylon ammodendron (H. ammodendron) faces the critical challenge of sustaining the growth and development of reproductive branches during hot and arid summers, which is essential for its seed set. Previous transcriptome analysis revealed higher expression of the NAC transcription factor gene HaNAC11 in reproductive branches compared to vegetative branches, suggesting its potential role in regulating the growth and development of reproductive branches under environmental stress. We found that HaNAC11 exhibited higher expression in flowers and reproductive branches and responded significantly to various stressors, such as drought, high salt, temperature extremes, as well as to treatments with different plant hormones including abscisic acid (ABA), salicylic acid (SA) and indole-3-acetic acid (IAA). Subsequent characterization confirmed that HaNAC11 encodes a nuclear-localized NAC transcription factor with homodimer formation capability and transcriptional activation activity. Heterologous expression of HaNAC11 in Arabidopsis enhanced plant adaptation to high-temperature and wind stress. Further transcriptome and KEGG pathway analyses revealed that under normal conditions, glycerolipid metabolism was upregulated in HaNAC11-transgenic Arabidopsis plants. Under high-temperature stress, pathways related to glycerolipid metabolism, particularly the biosynthesis of cutin, wax, suberin, and fatty acids, were further upregulated in the transgenic plants. Consistently, triacylglycerol, the end product of glycerolipid metabolism, accumulated significantly in transgenic Arabidopsis. Substantial triacylglycerol accumulation was also observed in the reproductive branches of H. ammodendron under desert conditions. Conversely, virus-induced gene silencing (VIGS) of HaNAC11 significantly reduced triacylglycerol accumulation in H. ammodendron reproductive branches. Heterologous expression of HaNAC11 may enhance thermotolerance and promote reproductive growth in Arabidopsis by regulating glycerolipid metabolism; in its native species H. ammodendron, HaNAC11 is likely to regulate triacylglycerol synthesis through a similar mechanism.