Roles of type II H+-PPases and PPsPase1/PECP2 in early developmental stages and PPi homeostasis of Arabidopsis thaliana

An analysis of lncRNAs related to fiber quality and the discovery of their target genes in a Gossypium hirsutum line with Gossypium mustelinum introgression

KEY MESSAGE

Analysis of fiber quality lncRNAs and their target genes from a pair of Gossypium mustelinum near-isogenic lines provide new prospects for improving the fiber quality of Upland cotton. Long noncoding RNAs (lncRNAs) are an important part of genome transcription and play roles in a wide range of biological processes in plants. In this research, a pair of near-isogenic cotton lines, namely, a Gossypium mustelinum introgression line (IL9) with outstanding fiber quality and its recurrent Upland cotton parent (PD94042), were used as the experimental materials. Cotton fibers were selected for lncRNA sequencing at 17 and 21 days post-anthesis. A total of 2693 differentially expressed genes were identified. In total, 5841 lncRNAs were ultimately screened, from which 163 differentially expressed lncRNAs were identified. Target genes of the lncRNAs were predicted by two different methods: cis and trans. Some of the target genes were related to cell components, membrane components, plant hormone signal transduction and catalytic metabolism, and the results indicated that there might also be important effects on the development of fiber. Four differentially expressed target genes related to fiber quality (Gomus.D05G015100, Gomus.A05G281300, Gomus.A12G023400 and Gomus.A10G226800) were screened through gene function annotation, and the functions of these four genes were verified through virus-induced gene silencing (VIGS). Compared to the negative controls, plants in which any of these four genes were silenced showed significant reductions in fiber strength. In addition, the plants in which the Gomus.A12G023400 gene was silenced showed a significant reduction in fiber uniformity, whereas the plants in which Gomus.A05G281300 was silenced showed a significant increase in fiber fineness as measured via micronaire. Our results showed that these genes play different roles during fiber development, impacting fiber quality.

Mutations in type II Golgi-localized proton pyrophosphatase AVP2;1/VHP2;1 affect pectic polysaccharide rhamnogalacturonan-II and alter root growth under low boron condition in Arabidopsis thaliana

The essential plant nutrient boron is required for the crosslinking of the pectin polysaccharide, rhamnogalacturonan II (RG-II). The synthesis of the pectic polysaccharides takes place in the Golgi apparatus, acidified by proton pumps. AVP2;1/VHP2;1 is a type II proton pyrophosphatase localized in the Golgi apparatus, which possesses proton pumping activity coupled with pyrophosphate hydrolysis. Its activity and expression patterns have been previously revealed but its role in plants remains unknown. The aim of the present work therefore was to explore the physiological role of AVP2;1 in Arabidopsis thaliana. In the screening of mutants under low boron, a mutant carrying a missense mutation in AVP2;1 was isolated. This mutant showed increased primary root growth under low boron conditions but no significant difference under normal boron condition compared to wild type plants. T-DNA insertion caused similar growth, suggesting that reduced function of AVP2;1 was responsible. Root cell observation revealed an increase in meristematic zone length, cell number in meristem and length of matured cell in avp2;1 mutants compared to wild type under low boron. Calcium concentration was reduced in mutant root cell wall under low boron. RG-II specific sugars also tended to be decreased in mutant root cell wall under low and normal boron conditions. These results suggest that changes in cell wall component by mutations in AVP2;1 may possibly explain the increased root length of mutants under low boron. This supports the idea that AVP2;1 plays a role in pH homoeostasis in Golgi apparatus for pectin synthesis.