Abstract
ABSTRACT Tea ( Camellia sinensis ) is a globally significant economic crop, and its desirable quality and health benefits are largely credited to catechin derivatives. Plant growth-promoting rhizobacteria (PGPR), such as Bacillus velezensis , are well-known for enhancing the environmental fitness and disease resistance of plants. However, the regulation of their impact on tea catechin biosynthesis remains unclear. While previous studies have focused on PGPR-facilitated growth promotion in crops like tomatoes and rice, the physiological mechanisms by which microbes regulate secondary metabolism in tea—especially under co-inoculation conditions—remain largely underexplored. This study examined the effects of B. velezensis SD24, isolated from tea rhizosphere soil, on catechin derivative accumulation of tea leaves by altering gene expression and the rhizosphere microbiome. Strain SD24 exhibited broad-spectrum antimicrobial activity against various pathogens due to behaving antimicrobial gene clusters. Tea plants inoculated with SD24 showed significantly increased levels of catechin derivatives in their leaves. This was likely achieved by upregulation of leucoanthocyanidin reductase and anthocyanidin reductase within the phenylpropanoid pathway. Additionally, chlorophyll content was increased. Transcriptomic analysis revealed a notable enrichment in biosynthesis of secondary natural products among the tea genes activated by SD24 inoculation. Metagenomic analysis further demonstrated that SD24 inoculation led to a restructuring of the tea rhizosphere microbiome. Notably, co-inoculation with Piriformospora indica , a beneficial endophytic fungus, suppressed SD24-induced gene expression and catechin accumulation, underscoring its antagonism toward SD24. These findings suggest that B. velezensis SD24 enhances tea quality, probably by transcriptionally activating the synthesis of catechin derivatives, a process associated with the restructuring of the rhizosphere microbiome. IMPORTANCE The mechanisms through which plant growth-promoting rhizobacteria (PGPR) influence secondary metabolism in perennial crops remain poorly understood. This study demonstrates that Bacillus velezensis SD24, a tea rhizosphere isolate, significantly enhances the accumulation of health-beneficial catechin derivatives in tea leaves. This quality improvement is associated with transcriptionally upregulating key biosynthetic genes ( LAR and ANR ) and concurrently restructuring the rhizosphere microbiome. Furthermore, we reveal a critical antagonistic interaction, where the beneficial fungus Piriformospora indica suppresses these SD24-induced effects. Our findings provide crucial insights into how specific PGPR strains may directly enhance tea quality by affecting host plant metabolism and the root microbiome, highlighting the complex and tailored microbial interactions that could be harnessed for sustainable agriculture.
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Claims 8
Claim · model-written summary
Bacillus velezensis SD24 exhibited broad antimicrobial activity against pathogens.
- Taxon
- Teae2
- Interactor
- various pathogense0pathogen
- Second interactor
- Bacillus velezensis SD24
Bacillus velezensise1biocontrol_agent - Outcome
- broad-spectrum antimicrobial activity against various pathogense0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Strain SD24 exhibited broad-spectrum antimicrobial activity against various pathogens due to behaving antimicrobial gene clusters.”
e1“Bacillus velezensis SD24”
e2“Tea plants”
Claim · model-written summary
SD24 inoculation significantly increased catechin derivatives in tea leaves.
- Taxon
- Teae0
- Organ / stage
- leavese0
- Treatment
- inoculated with SD24e0
- Interactor
- Bacillus velezensis SD24Bacillus velezensise1symbiont
- Outcome
- levels of catechin derivativese0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Tea plants inoculated with SD24 showed significantly increased levels of catechin derivatives in their leaves.”
e1“Bacillus velezensis SD24”
Claim · model-written summary
SD24 inoculation increased tea leaf chlorophyll content.
- Taxon
- Teae1
- Treatment
- inoculated with SD24e1
- Interactor
- Bacillus velezensis SD24Bacillus velezensise2symbiont
- Outcome
- chlorophyll contente0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Additionally, chlorophyll content was increased.”
e1“Tea plants inoculated with SD24”
e2“Bacillus velezensis SD24”
Claim · model-written summary
SD24 inoculation was associated with upregulation of leucoanthocyanidin reductase and anthocyanidin reductase.
- Taxon
- Teae1
- Interactor
- Bacillus velezensis SD24Bacillus velezensise2symbiont
- Gene
- leucoanthocyanidin reductase and anthocyanidin reductasee0
- Outcome
- upregulation of leucoanthocyanidin reductase and anthocyanidin reductasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This was likely achieved by upregulation of leucoanthocyanidin reductase and anthocyanidin reductase within the phenylpropanoid pathway.”
e1“Tea plants inoculated with SD24”
e2“Bacillus velezensis SD24”
Claim · model-written summary
Tea genes activated by SD24 were enriched for secondary natural product biosynthesis.
- Taxon
- teae0
- Interactor
- Bacillus velezensis SD24Bacillus velezensise1symbiont
- Gene
- tea genese0
- Outcome
- notable enrichment in biosynthesis of secondary natural productse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcriptomic analysis revealed a notable enrichment in biosynthesis of secondary natural products among the tea genes activated by SD24 inoculation.”
e1“Bacillus velezensis SD24”
Claim · model-written summary
SD24 inoculation restructured the tea rhizosphere microbiome.
- Taxon
- teae0
- Treatment
- SD24 inoculatione0
- Interactor
- Bacillus velezensis SD24Bacillus velezensise1symbiont
- Outcome
- restructuring of the tea rhizosphere microbiomee0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SD24 inoculation led to a restructuring of the tea rhizosphere microbiome.”
e1“Bacillus velezensis SD24”
Claim · model-written summary
Co-inoculation with Piriformospora indica suppressed SD24-induced tea gene expression.
- Taxon
- teae1
- Treatment
- co-inoculation with Piriformospora indicae0
- Interactor
- Piriformospora indicaSerendipita indicae0symbiont
- Second interactor
- Bacillus velezensis SD24Bacillus velezensise2symbiont
- Outcome
- gene expressione0
- Direction
- suppressede0
- Comparator
- SD24-inducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“co-inoculation with Piriformospora indica , a beneficial endophytic fungus, suppressed SD24-induced gene expression and catechin accumulation”
e1“tea genes activated by SD24 inoculation”
e2“Bacillus velezensis SD24”
Claim · model-written summary
Co-inoculation with Piriformospora indica suppressed SD24-induced tea catechin accumulation.
- Taxon
- teae1
- Treatment
- co-inoculation with Piriformospora indicae0
- Interactor
- Piriformospora indicaSerendipita indicae0symbiont
- Second interactor
- Bacillus velezensis SD24Bacillus velezensise2symbiont
- Outcome
- catechin accumulatione0
- Direction
- suppressede0
- Comparator
- SD24-inducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“co-inoculation with Piriformospora indica , a beneficial endophytic fungus, suppressed SD24-induced gene expression and catechin accumulation”
e1“tea genes activated by SD24 inoculation”
e2“Bacillus velezensis SD24”
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