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Title: Phytohormonal networks promote differentiation of fiber initials on pre-anthesis cotton ovules grown in vitro and in planta

item Kim, Hee-Jin
item Hinchliffe, Doug
item Triplett, Barbara
item CHEN, Z - University Of Texas At Austin
item STELLY, DAVID - Texas A&M University
item Yeater, Kathleen
item Moon, Hong
item Gilbert, Matthew
item Thyssen, Gregory
item Turley, Rickie
item Fang, David

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2015
Publication Date: 4/30/2015
Citation: Kim, H.J., Hinchliffe, D.J., Triplett, B.A., Chen, Z.J., Stelly, D.M., Yeater, K.M., Moon, H.S., Gilbert, M.K., Thyssen, G.N., Turley, R.B., Fang, D.D. 2015. Phytohormonal networks promote differentiation of fiber initials on pre-anthesis cotton ovules grown in vitro and in planta. PLoS ONE. 10(4):e0125046.

Interpretive Summary: How and when fiber initiation occurs on cotton ovules is an important question for biologists, cotton producers, and textile industry since the density and numbers of fibers on the surface of cotton ovules directly affect cotton yield and fiber quality. Despite its importance, molecular mechanisms regulating cotton fiber initiation are mostly unknown due to technical difficulties in monitoring the rapid process of fiber initial differentiation in cotton ovaries. To understand molecular mechanisms affecting fiber initiation process, we optimized culture conditions for controlling the timing of fiber initiation process on the surface of cotton ovules grown in Petri dishes. With the controlled conditions, we enabled to identify candidate genes involved in fiber initiation process. Those candidate genes were verified with wild type cotton and three fiberless mutants grown in the field. Various plant hormones and their signaling networks regulated the expression of genes responsible for fiber initiation process. The results provide an insight on molecular mechanisms controlling when and how fiber initiation occurs on cotton ovules. Thus, the ability to manipulate the expression of genes regulating fiber initiation process may lead to strategies for improving cotton yield and fiber quality.

Technical Abstract: The number of cotton (Gossypium sp.) ovule epidermal cells differentiating into fiber initials is an important factor affecting cotton yield and fiber quality. Despite extensive efforts in determining the molecular mechanisms regulating fiber initial differentiation, only a few genes responsible for fiber initial differentiation have been discovered. To identify putative genes directly involved in the fiber initiation process, we used a cotton ovule culture technique that controls the timing of fiber initial differentiation by exogenous phytohormone application in combination with comparative expression analyses between wild type and three fiberless mutants. The addition of exogenous auxin and gibberellins to pre-anthesis wild type ovules that did not have visible fiber initials increased the expression of genes affecting auxin, ethylene, ABA and jasmonic acid signaling pathways within 1 h after treatment. Most transcripts expressed differentially by the phytohormone treatment in vitro were also differentially expressed in the ovules of wild type and fiberless mutants that were grown in planta. In addition to GhMyb25-like, a gene that was previously shown to be associated with the differentiation of fiber initials, several other differentially expressed genes, including auxin/indole-3-acetic acid (AUX/IAA) involved in auxin signaling, ACC oxidase involved in ethylene biosynthesis, and abscisic acid (ABA) 8'-hydroxylase an enzyme that controls the rate of ABA catabolism, were co-regulated in the pre-anthesis ovules of both wild type and fiberless mutants. These results support the hypothesis that phytohormonal signaling networks regulate the temporal expression of genes responsible for differentiation of cotton fiber initials in vitro and in planta.