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RNA-seq analysis of short fiber mutants Ligon-lintless-1 (Li 1 ) and - 2 (Li 2 ) revealed important role of aquaporins in cotton (Gossypium hirsutum L.) fiber elongation.

Naoumkina M, Thyssen GN, Fang DD - BMC Plant Biol. (2015)

Bottom Line: We found a large number of differentially expressed genes common to both mutants, including 531 up-regulated genes and 652 down-regulated genes.We found that the aquaporins were the most down-regulated gene family in both short fiber mutants.These results suggest that higher accumulation of ions in fiber cells, reduced osmotic pressure and low expression of aquaporins, may contribute to the cessation of fiber elongation in Li 1 and Li 2 short-fiber mutants.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Cotton fiber length is a key determinant of fiber quality for the textile industry. Understanding the molecular basis of fiber elongation would provide a means for improvement of fiber length. Ligon lintless-1 (Li 1 ) and Ligon lintless-2 (Li 2 ) are monogenic and dominant mutations, that result in an extreme reduction in the length of lint fiber to approximately 6 mm on mature seeds. In a near-isogenic state with wild type (WT) cotton these two short fiber mutants provide an excellent model system to study mechanisms of fiber elongation.

Results: We used next generation sequencing (RNA-seq) to identify common fiber elongation related genes in developing fibers of Li 1 and Li 2 mutants growing in the field and a greenhouse. We found a large number of differentially expressed genes common to both mutants, including 531 up-regulated genes and 652 down-regulated genes. Major intrinsic proteins or aquaporins were one of the most significantly over-represented gene families among common down-regulated genes in Li 1 and Li 2 fibers. The members of three subfamilies of aquaporins, including plasma membrane intrinsic proteins, tonoplast intrinsic proteins and NOD26-like intrinsic proteins were down-regulated in short fiber mutants. The osmotic concentration and the concentrations of soluble sugars were lower in fiber cells of both short fiber mutants than in WT, whereas the concentrations of K+ and malic acid were significantly higher in mutants during rapid cell elongation.

Conclusions: We found that the aquaporins were the most down-regulated gene family in both short fiber mutants. The osmolality and concentrations of soluble sugars were less in saps of Li 1 - Li 2 , whereas the concentrations of malic acid, K+ and other detected ions were significantly higher in saps of mutants than in WT. These results suggest that higher accumulation of ions in fiber cells, reduced osmotic pressure and low expression of aquaporins, may contribute to the cessation of fiber elongation in Li 1 and Li 2 short-fiber mutants. The research presented here provides new insights into osmoregulation of short fiber mutants and the role of aquaporins in cotton fiber elongation.

Show MeSH
A possible mechanism of termination of fiber elongation in theLi1andLi2mutants. The high osmotic pressure in fiber cell of WT and high level of expression of aquaporins facilitates influx of water that contributes to the rapid fiber elongation. The higher accumulation of ions in fiber cells of Li1 – Li2 may be the result of limited uptake of water. The reduced influx of water (due to low concentration of sugars and low expression of aquaporins) causes the reduced fiber elongation in the Li1 – Li2 mutants.
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Fig6: A possible mechanism of termination of fiber elongation in theLi1andLi2mutants. The high osmotic pressure in fiber cell of WT and high level of expression of aquaporins facilitates influx of water that contributes to the rapid fiber elongation. The higher accumulation of ions in fiber cells of Li1 – Li2 may be the result of limited uptake of water. The reduced influx of water (due to low concentration of sugars and low expression of aquaporins) causes the reduced fiber elongation in the Li1 – Li2 mutants.

Mentions: The driving force for the transport and accumulation of ions into the protoplast and vacuole is provided by the plasma membrane and vacuolar H+-ATPases [27,31]. We did not detect the plasma membrane and vacuolar H+-ATPases among common Li1 – Li2 up-regulated or down-regulated pools of genes. Numbers of calcium, potassium and other metal transporters were not significantly different between pools of up-regulated and down-regulated genes in short fiber mutants; except for sulphate and phosphate transporters which were present among down-regulated genes only (Tables 1 and 2). Thus, ion transport in Li1 – Li2 is unlikely to be affected by the mutations and proceeds normally as in wild type plants. The higher concentrations of malic acid, K+ and other inorganic ions detected in sap of Li1 – Li2 can be explained by reduced influx of water into fiber cells of mutants (Figure 5). Since malic acid and K+ (major osmotic solutes) cannot restore the balance of water uptake into developing Li1 – Li2 fibers, there is another factor, which might be crucial for osmoregulation of cotton fibers – the major intrinsic proteins (Figure 6).Figure 6


RNA-seq analysis of short fiber mutants Ligon-lintless-1 (Li 1 ) and - 2 (Li 2 ) revealed important role of aquaporins in cotton (Gossypium hirsutum L.) fiber elongation.

Naoumkina M, Thyssen GN, Fang DD - BMC Plant Biol. (2015)

A possible mechanism of termination of fiber elongation in theLi1andLi2mutants. The high osmotic pressure in fiber cell of WT and high level of expression of aquaporins facilitates influx of water that contributes to the rapid fiber elongation. The higher accumulation of ions in fiber cells of Li1 – Li2 may be the result of limited uptake of water. The reduced influx of water (due to low concentration of sugars and low expression of aquaporins) causes the reduced fiber elongation in the Li1 – Li2 mutants.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4352256&req=5

Fig6: A possible mechanism of termination of fiber elongation in theLi1andLi2mutants. The high osmotic pressure in fiber cell of WT and high level of expression of aquaporins facilitates influx of water that contributes to the rapid fiber elongation. The higher accumulation of ions in fiber cells of Li1 – Li2 may be the result of limited uptake of water. The reduced influx of water (due to low concentration of sugars and low expression of aquaporins) causes the reduced fiber elongation in the Li1 – Li2 mutants.
Mentions: The driving force for the transport and accumulation of ions into the protoplast and vacuole is provided by the plasma membrane and vacuolar H+-ATPases [27,31]. We did not detect the plasma membrane and vacuolar H+-ATPases among common Li1 – Li2 up-regulated or down-regulated pools of genes. Numbers of calcium, potassium and other metal transporters were not significantly different between pools of up-regulated and down-regulated genes in short fiber mutants; except for sulphate and phosphate transporters which were present among down-regulated genes only (Tables 1 and 2). Thus, ion transport in Li1 – Li2 is unlikely to be affected by the mutations and proceeds normally as in wild type plants. The higher concentrations of malic acid, K+ and other inorganic ions detected in sap of Li1 – Li2 can be explained by reduced influx of water into fiber cells of mutants (Figure 5). Since malic acid and K+ (major osmotic solutes) cannot restore the balance of water uptake into developing Li1 – Li2 fibers, there is another factor, which might be crucial for osmoregulation of cotton fibers – the major intrinsic proteins (Figure 6).Figure 6

Bottom Line: We found a large number of differentially expressed genes common to both mutants, including 531 up-regulated genes and 652 down-regulated genes.We found that the aquaporins were the most down-regulated gene family in both short fiber mutants.These results suggest that higher accumulation of ions in fiber cells, reduced osmotic pressure and low expression of aquaporins, may contribute to the cessation of fiber elongation in Li 1 and Li 2 short-fiber mutants.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Cotton fiber length is a key determinant of fiber quality for the textile industry. Understanding the molecular basis of fiber elongation would provide a means for improvement of fiber length. Ligon lintless-1 (Li 1 ) and Ligon lintless-2 (Li 2 ) are monogenic and dominant mutations, that result in an extreme reduction in the length of lint fiber to approximately 6 mm on mature seeds. In a near-isogenic state with wild type (WT) cotton these two short fiber mutants provide an excellent model system to study mechanisms of fiber elongation.

Results: We used next generation sequencing (RNA-seq) to identify common fiber elongation related genes in developing fibers of Li 1 and Li 2 mutants growing in the field and a greenhouse. We found a large number of differentially expressed genes common to both mutants, including 531 up-regulated genes and 652 down-regulated genes. Major intrinsic proteins or aquaporins were one of the most significantly over-represented gene families among common down-regulated genes in Li 1 and Li 2 fibers. The members of three subfamilies of aquaporins, including plasma membrane intrinsic proteins, tonoplast intrinsic proteins and NOD26-like intrinsic proteins were down-regulated in short fiber mutants. The osmotic concentration and the concentrations of soluble sugars were lower in fiber cells of both short fiber mutants than in WT, whereas the concentrations of K+ and malic acid were significantly higher in mutants during rapid cell elongation.

Conclusions: We found that the aquaporins were the most down-regulated gene family in both short fiber mutants. The osmolality and concentrations of soluble sugars were less in saps of Li 1 - Li 2 , whereas the concentrations of malic acid, K+ and other detected ions were significantly higher in saps of mutants than in WT. These results suggest that higher accumulation of ions in fiber cells, reduced osmotic pressure and low expression of aquaporins, may contribute to the cessation of fiber elongation in Li 1 and Li 2 short-fiber mutants. The research presented here provides new insights into osmoregulation of short fiber mutants and the role of aquaporins in cotton fiber elongation.

Show MeSH