NAC Transcription Factor LpNAC22 Positively Regulates Drought Tolerance in Perennial Ryegrass

Drought serves as a major environmental stress that restricts both the yield and quality of perennial ryegrass. Therefore, it is important to identify the essential genes that determine drought tolerance in perennial ryegrasses. In this paper, we isolated a drought-induced NAC transcription factor LpNAC22. Transcriptional activity assays in yeast and plant cells indicated that LpNAC22 has transcriptional activation function. Subcellular localization observations revealed that LpNAC22 localized in the nucleus, compatible with its function as a transcription factor. LpNAC22 overexpression plants had enhanced drought tolerance and reduced cell membrane damage, whereas the knockdown of LpNAC22 in perennial ryegrass reduced plant drought tolerance and led to aggravated cell membrane damage. Late embryogenesis abundant (LEA), well-known stress resistance proteins, can protect the cell membrane from damage during drought conditions. DNA affinity purification sequencing and transcriptional regulation analysis demonstrated that LpNAC22 upregulates two LEA family genes, LpLEA1 and LpLEA2-1, by directly binding to their promoters. Furthermore, we demonstrated that overexpression of LpLEA1 and LpLEA2-1 in Arabidopsis enhanced drought tolerance and reduced cell membrane damage under drought conditions. Our findings provide evidence that LpNAC22 improves drought resistance by modulating the transcription of LEA family genes in perennial ryegrass.