Study on Gene Differential Expression in Tetraploid Populus Leaves

Polyploids exhibit different phenotypes compared to those of diploids in plants, and the important role of polyploids in tree breeding has been widely recognized. The transcriptomes detected by RNA-seq in the Populus triploid by doubling the chromosomes of the female gamete, in the triploid by doubling the chromosomes of somatic cells and the diploid with the parent were compared to reveal the patterns of gene expression of tetraploid leaves and their influence on growth. The results showed that the high expression of GATA and PORA in tetraploid leaves was the reason for the higher chlorophyll content in the leaves than in diploid and triploid leaves. The 11-day-old tetraploid leaves began to enter the aging stage. Compared with that in the diploid, GRF was significantly upregulated, while the amylase genes were downregulated. Compared with those in the triploid, 3 STN7 genes that regulate photosynthetic genes and PGSIP genes which are related to starch synthesis, were significantly downregulated in the tetraploid, and the auxin receptor protein TIR1 was also significantly downregulated. In the tetraploid, auxin-regulating genes such as GH3 and AUX/IAA as well as genes involved in the regulation of leaf senescence, SAG genes and SRG genes were significantly up-regulated, resulting in a decrease in the auxin content. In senescent leaves, CHLD, CHLI1, and CHLM in the early stage of chlorophyll synthesis all began to downregulate their expressions, leading to the downregulation of LHC genes and a decrease in their photosynthetic efficiency, which led to the downregulation of carbon fixation-related genes such as SS genes, thus affecting carbon synthesis and fixation. This finally led to the slow growth of tetraploid plants. These data represent the transcriptome characteristics of tetraploid, and they can be used as a resource for further research on polyploids and provide a reference for further understanding of the function of polyploid vegetative growth-related genes.

Genome Wide Identification and Characterization of Light-Harvesting Chloro a/b Binding Genes Reveals their Potential Role in Enhancing Drought Tolerance in Gossypium hirsutum

BackgroundCotton is an important commercial crop for its valuable source of natural fiber. Its production has undergone a sharp failure because of abiotic stress influences, of significance is drought. Moreover, plants have evolved self-defense mechanisms against the effects of several ways of abiotic factors like drought, salt, cold among others. The evolution of stress responsive transcription factors such as the trihelix, a nodule-inception-like protein (NLP), the late embryogenesis abundant (LEA) proteins among others have shown positive response in improving resistance to several forms of abiotic stress features.ResultsGenome wide identification and characterization of the effects of Light-Harvesting Chloro a/b binding (LHC) genes was carried out in cotton under drought stress conditions. A hundred and nine proteins encoded by the LHC genes were found in the cotton genome, with 55, 27, and 27 genes found to be distributed in Gossypium hirsutum, G. arboreum, and G. raimondii, respectively. The proteins encoded by the genes were unevenly distributed in various chromosomes. The Ka/Ks values were less than one, and an indication of negative selection of the gene family. differential expression arrangement of genes was showed with the majority of the genes being highly upregulated in the root tissues in relative to leave and stem tissues. Moreover, more genes were induced in M85 a relative drought tolerant germplasm.Conclusion:The results provide proof of the possible role of the LHC genes in improving drought stress tolerance, and can be explored by cotton breeders in releasing a more drought tolerant cotton germplasms.

On the Expression of Several Lhc Genes in Garden Cress (Lepidium sativum L.)

The polymerase chain reaction was used to prepare gene-specific probes for several Lhc genes coding for chlorophyll a/b-binding proteins of cress (Lepidium sativum L.). Due to the presence of about 150 basepairs of the coding region, the isolated clones could be attributed to Lhc a3 (1 clone), Lhc b1 (5 clones), Lhc b2 (1 clone) and Lhc b3 (1 clone) genes. Probes prepared from the 3′ non-coding regions of the clones did not cross-hybridize; they were specific for 3 different Lhc b1 transcripts and one each of Lhc b2, Lhc b3 and Lhc a 3 transcripts. The transcript levels were higher in leaves than in cotyledons of light-grown seedlings; they decreased significantly in cotyledons from week 1 to week 4. The levels of 2 Lhc b1 transcripts (detected with probes cd 1 and cd 2) changed from 1 week old cotyledons (30% c d l, 28% cd 2) to 3 months old leaves (14% c d l), 44% cd 2), stems (11% c d l, 56% cd 2) and fruits (15% cd 1, 62% cd 2, all values percent of total transcripts), whereas transcript levels of another Lhc b1 gene (detected with probe cd 3) and of a Lhc a 3 gene remained nearly constant. The level of Lhc b2 and Lhc b3 transcripts were 1 - 2 orders of magnitude smaller than those of the other Lhc transcripts. The data obtained with cress plants are compared with published data from other plants.