Abstract
As the second most abundant natural polymer, accounting for approximately 30% of the organic carbon in the biosphere, lignin plays an essential role in plant development. However, a high lignin content affects the nutritional quality of alfalfa (Medicago sativa L.), the most widely cultivated perennial legume forage crop. Histological analysis indicated that G-lignin and S-lignin were present in the stem, leaf, and petiole of alfalfa, and the deposition of lignin increased gradually in descending internodes. Neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) contents continually increased from the top to the bottom of the stem, and ADL content showed a similar trend in leaves. Alfalfa leaves and stems from five different nodes (1, 2, 4, 6, and 8) were used as materials to investigate molecular regulatory mechanisms in lignin synthesis by RNA sequencing. Respectively 8074 and 7752 differentially expressed genes (DEGs) were identified in leaves and stems, and 1694 DEGs were common to the two tissues. “Phenylpropanoid biosynthesis” was the most enriched pathway in both leaves and stems, and 134 key regulatory genes in lignin synthesis were identified by a weighted gene co-expression network analysis. The NAC family transcription factor MsNST1 gene was highly expressed in old leaf and stem tissues. The deposition pattern of G- and S-lignin differed among M. truncatula wild-type, nst1 mutants, and overexpression lines, and the transcription levels of lignin synthesis genes such as HCT, F5H, and COMT in these three materials also differed. These results suggest that MsNST1 affects lignin synthesis in alfalfa. These findings provide a genetic basis and abundant gene resources for further study of the molecular mechanisms of lignin synthesis, laying a foundation for low-lignin alfalfa breeding research.
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Claims 13
Claim · model-written summary
G-lignin and S-lignin occurred in alfalfa stems, leaves and petioles.
- Taxon
- alfalfa
Medicago sativae0 - Organ / stage
- stem, leaf, and petiolee0
- Outcome
- G-lignin and S-lignin were presente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“G-lignin and S-lignin were present in the stem, leaf, and petiole of alfalfa”
Claim · model-written summary
Lignin deposition rose in descending internodes.
- Taxon
- alfalfaMedicago sativae1
- Organ / stage
- descending internodese0
- Outcome
- deposition of lignine0
- Direction
- increased graduallye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the deposition of lignin increased gradually in descending internodes”
e1“petiole of alfalfa”
Claim · model-written summary
NDF, ADF and ADL increased from top to bottom of the stem.
- Taxon
- alfalfaMedicago sativae1
- Organ / stage
- steme0
- Outcome
- Neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) contentse0
- Direction
- continually increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) contents continually increased from the top to the bottom of the stem”
e1“petiole of alfalfa”
Claim · model-written summary
Leaf ADL content followed a similar increase.
- Taxon
- alfalfaMedicago sativae2
- Organ / stage
- leavese0
- Outcome
- ADL contente0
- Direction
- increasede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ADL content showed a similar trend in leaves”
e1“contents continually increased from the top to the bottom of the stem”
e2“petiole of alfalfa”
Claim · model-written summary
RNA sequencing identified 8074 leaf DEGs.
- Taxon
- AlfalfaMedicago sativae1
- Organ / stage
- leavese0
- Outcome
- differentially expressed genes (DEGs)e0
- Value
- 8074e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Respectively 8074 and 7752 differentially expressed genes (DEGs) were identified in leaves and stems”
e1“Alfalfa leaves and stems”
Claim · model-written summary
RNA sequencing identified 7752 stem DEGs.
- Taxon
- AlfalfaMedicago sativae1
- Organ / stage
- stemse0
- Outcome
- differentially expressed genes (DEGs)e0
- Value
- 7752e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Respectively 8074 and 7752 differentially expressed genes (DEGs) were identified in leaves and stems”
e1“Alfalfa leaves and stems”
Claim · model-written summary
There were 1694 DEGs shared by leaves and stems.
- Taxon
- AlfalfaMedicago sativae1
- Outcome
- DEGs were common to the two tissuese0
- Value
- 1694e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“1694 DEGs were common to the two tissues”
e1“Alfalfa leaves and stems”
Claim · model-written summary
Phenylpropanoid biosynthesis was the most enriched pathway in leaves and stems.
- Taxon
- AlfalfaMedicago sativae1
- Organ / stage
- leaves and stemse0
- Outcome
- “Phenylpropanoid biosynthesis” was the most enriched pathwaye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0““Phenylpropanoid biosynthesis” was the most enriched pathway in both leaves and stems”
e1“Alfalfa leaves and stems”
Claim · model-written summary
Network analysis identified 134 key lignin regulatory genes.
- Taxon
- AlfalfaMedicago sativae1
- Outcome
- key regulatory genes in lignin synthesise0
- Value
- 134e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“134 key regulatory genes in lignin synthesis were identified by a weighted gene co-expression network analysis”
e1“Alfalfa leaves and stems”
Claim · model-written summary
MsNST1 was highly expressed in old leaves and stems.
- Taxon
- AlfalfaMedicago sativae1
- Organ / stage
- old leaf and stem tissuese0
- Gene
- MsNST1e0
- Outcome
- highly expressede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The NAC family transcription factor MsNST1 gene was highly expressed in old leaf and stem tissues.”
e1“Alfalfa leaves and stems”
Claim · model-written summary
G- and S-lignin deposition differed across wild type, nst1 mutants and overexpression lines.
- Taxon
- M. truncatula
Medicago truncatulae0 - Material
- nst1 mutantse0
- Outcome
- deposition pattern of G- and S-lignine0
- Direction
- differede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The deposition pattern of G- and S-lignin differed among M. truncatula wild-type, nst1 mutants, and overexpression lines”
Claim · model-written summary
Lignin synthesis gene transcription differed among those materials.
- Taxon
- M. truncatulaMedicago truncatulae1
- Material
- nst1 mutantse1
- Gene
- HCT, F5H, and COMTe0
- Outcome
- transcription levelse0
- Direction
- differede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the transcription levels of lignin synthesis genes such as HCT, F5H, and COMT in these three materials also differed”
e1“M. truncatula wild-type, nst1 mutants, and overexpression lines”
Claim · model-written summary
Authors infer MsNST1 affects alfalfa lignin synthesis.
- Taxon
- alfalfaMedicago sativae0
- Gene
- MsNST1e0
- Outcome
- lignin synthesise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“These results suggest that MsNST1 affects lignin synthesis in alfalfa.”