Mining core genes for low-phosphorus tolerance in barley leaves based on WGCNA and analysis of the HPT gene family

Phosphorus deficiency is a major abiotic stress limiting crop growth, and mining low-phosphorus tolerance genes is crucial for breeding phosphorus-efficient varieties. In this study, phosphorus-efficient barley GN121 was used as material to reanalyze leaf transcriptome data under low-phosphorus stress. Differentially expressed genes (DEGs) were screened at 3, 19 and 23 days of stress, with a total of 4,043 non-redundant DEGs obtained. Weighted Gene Co-expression Network Analysis (WGCNA) divided these DEGs into 14 modules, and the MEbrown module (492 genes) was identified as the key module with extremely significant positive correlation with leaf phosphorus content (r=0.75, P = 3.2×10 -4 ). HvHPT4 encoding homogentisate phytyltransferase (HPT) was screened as the key hub gene. Genome-wide identification revealed 5 HPT family members ( HvHPT1 - HvHPT5 ) in barley, distributed on 1H, 2H and 7H chromosomes, all encoding hydrophobic transmembrane proteins with structural differentiation. Promoter cis-acting element analysis showed HvHPT genes contained various stress and hormone response elements, with HvHPT3 having the most stress-related elements. Expression profiles were inspected for four abiotic-stress conditions. RT-qPCR assays in this study confirmed that HvHPT3 and HvHPT4 respond to low-phosphorus and drought stress. Additional expression trends for osmotic and zinc stress were obtained from the public BarleyExpDB database and were not independently validated in our wet-lab experiments. Other family members exhibited stress-specific expression patterns under the tested conditions. This study constructed the low-phosphorus stress response gene co-expression network in barley leaves, clarified the characteristics and expression patterns of the HPT gene family, and revealed the key role of HvHPT3 and HvHPT4 in abiotic stress cross-response, providing candidate gene resources and a theoretical reference for further exploring crop phosphorus-efficiency genetic improvement.