Phytochrome RNAi enhances major fibre quality and agronomic traits of the cotton Gossypium hirsutum L

Abstract

Simultaneous improvement of fibre quality, early-flowering, early-maturity and productivity in Upland cotton (G. hirsutum) is a challenging task for conventional breeding. The influence of red/far-red light ratio on the fibre length prompted us to examine the phenotypic effects of RNA interference (RNAi) of the cotton PHYA1 gene. Here we show a suppression of up to B70% for the PHYA1 transcript, and compensatory overexpression of up to B20-fold in the remaining phytochromes in somatically regenerated PHYA1 RNAi cotton plants. Two independent transformants of three generations exhibited vigorous root and vegetative growth, early-flowering, significantly improved upper half mean fibre length and an improvement in other major fibre characteristics. Small decreases in lint traits were observed but seed cotton yield was increased an average 10-17% compared with controls. RNAi-associated phenotypes were heritable and transferable via sexual hybridization. These results should aid in the development of early-maturing and productive Upland cultivars with superior fibre quality.

Transcriptome Analysis of Ten-DPA Fiber in an Upland Cotton (<i>Gossypium hirsutum</i>) Line with Improved Fiber Traits from Phytochrome A1 RNAi Plants

“…The newest CYPs are involved in the synthesis of structural components such as lignin, fatty acid, pigments, odorants and signaling compounds [54]. Besides with improved fiber quality, PHYA1 RNAi plants have vigorous root and vegetative growth, and early flowering due to increased photosynthesis [6] [7]. CYPs are light-driven oxidase enzymes in electron transfer chains [55].…”

“…The RNAi construct was then somatically transformed into embryogenic Gossypium hirsutum L. cv. Coker 312 to generate transgenic cotton plants [6]. The resulting PHYA1-specific single-seed decent RNAi transgenic plants were subsequently self-pollinated through first to sixth generations (T1-7-6) and followed by selection of individu- …”

“…The PHYA1 RNAi cotton was reported to have a 5% increase in fiber length compared to non-transformed Coker 312 [6]. pectin, xyloglucan, lignin and hydroxyproline-rich glycoprotein [32].…”

“…With the aim to analyze the function of phytochrome A1 gene (PHYA1) of cotton in association with fiber length [15], a binary RNAi construct was previously developed by PCR amplification of the 213 bp hinge region of PHYA1 gene from G. hirsutum TM-1 genomic DNA and cloned into the PHellsgate-8 vector using the Gateway Cloning System (Thermo Fisher Scientific) [6]. The RNAi construct was then somatically transformed into embryogenic Gossypium hirsutum L. cv.…”

“…Previous studies showed that silencing phytochrome A1 gene (PHYA1) by RNA interference generated RNAi cotton lines with improved fiber quality (longer, stronger and finer fiber) and some other phenotypic changes, including early-flowering, vigorous root and vegetative growth, without adverse effects on yield and fiber development, and higher tolerance to abiotic stresses when compared to non-transformed Coker 312 [6] [7]. Phytochromes are red and far-red light photoreceptors, and a high ratio of far-red light to red light perceived by the photoreceptors increased fiber length [8].…”