Gibberellin Regulates LBD38-1 Responses to Xanthomonas arboricola pv. juglandis Infection in Walnut Bacterial Blight Pathogenesis.

BACKGROUND

Plant responses to biotic and abiotic stresses are complex processes. Previous studies have shown that the LBD gene family plays important roles in plant growth and development as well as in plant defense against biotic and abiotic stresses. The expression of LBD genes was investigated in walnuts under biotic and abiotic stresses, revealing that LBD38-1 may be a key gene in the plant stress response. This study provides new insights into the roles of LBD genes in plant responses to biotic stress.

RESULTS

Forty-nine members of the JrLBD gene family were identified in the walnut genome and classified into six subfamilies. Comparative homology analysis through phylogenetic trees revealed that the presence of Group I-a and Group VI plays an important role in resistance to stressors. The expression of walnut LBD genes under cold-temperature, high-temperature, mechanical damage, and biotic stresses was analyzed via transcriptome sequencing, and the expression of JrLBD38-1 in the Group VI subfamily was particularly prominent. According to transcriptome profile analysis, JrLBD38-1 is highly expressed in different tissues of walnuts, suggesting that it plays a regulatory role in the growth and development of different tissues. The function of the Gibberellin (GA) response element in the JrLBD38-1 promoter was further analyzed and verified. These findings confirmed that GA regulated JrLBD38-1 expression changes during Xanthomonas arboricola pv. juglandis infestation of walnut leaves.

CONCLUSION

Forty-nine walnut JrLBDs were identified and classified into six subfamilies. JrLBD38-1 has GA-inducible expression, is regulated by GA under pathogenic bacterial stress, and is involved in the response to biotic stress. This function of JrLBD38-1 provides new insights into walnut disease resistance mechanisms.