Cytogenetic analysis of Bienertia sinuspersici Akhani as the first step in genome sequencing

In-silico, evolutionary, and functional analysis of CHUP1 and its related proteins in Bienertia sinuspersici-a comparative study across C3, C4, CAM, and SCC4 model plants

Single-cell C₄ (SCC₄) plants with bienertioid anatomy carry out photosynthesis in a single cell. Chloroplast movement is the underlying phenomenon, where chloroplast unusual positioning 1 (CHUP1) plays a key role. This study aimed to characterize CHUP1 and CHUP1-like proteins in an SCC₄ photosynthetic plant, Bienertia sinuspersici. Also, a comparative analysis of SCC4 CHUP1 was made with C₃, C₄, and CAM model plants including an extant basal angiosperm, Amborella. The CHUP1 gene exists as a single copy from the basal angiosperms to SCC₄ plants. Our analysis identified that Chenopodium quinoa, a recently duplicated allotetraploid, has two copies of CHUP1. In addition, the numbers of CHUP1-like and its associated proteins such as CHUP1-like_a, CHUP1-like_b, HPR, TPR, and ABP varied between the species. Hidden Markov Model analysis showed that the gene size of CHUP1-like_a and CHUP1-like_b of SCC₄ species, Bienertia, and Suaeda were enlarged than other plants. Also, we identified that CHUP1-like_a and CHUP1-like_b are absent in Arabidopsis and Amborella, respectively. Motif analysis identified several conserved and variable motifs based on the orders (monocot and dicot) as well as photosynthetic pathways. For instance, CAM plants such as pineapple and cactus shared certain motifs of CHUP1-like_a irrespective of their distant phylogenetic relationship. The free ratio model showed that CHUP1 maintained purifying selection, whereas CHUP1-like_a and CHUP1-like_b have adaptive functions between SCC₄ plants and quinoa. Similarly, rice and maize branches displayed functional diversification on CHUP1-like_b. Relative gene expression data showed that during the subcellular compartmentalization process of Bienertia, CHUP1 and actin-binding proteins (ABP) genes showed a similar pattern of expression. Altogether, the results of this study provide insight into the evolutionary and functional details of CHUP1 and its associated proteins in the development of the SCC₄ system in comparison with other C₃, C₄, and CAM model plants.

Interstitial Telomeric-like Repeats (ITR) in Seed Plants as Assessed by Molecular Cytogenetic Techniques: A Review

The discovery of telomeric repeats in interstitial regions of plant chromosomes (ITRs) through molecular cytogenetic techniques was achieved several decades ago. However, the information is scattered and has not been critically evaluated from an evolutionary perspective. Based on the analysis of currently available data, it is shown that ITRs are widespread in major evolutionary lineages sampled. However, their presence has been detected in only 45.6% of the analysed families, 26.7% of the sampled genera, and in 23.8% of the studied species. The number of ITR sites greatly varies among congeneric species and higher taxonomic units, and range from one to 72 signals. ITR signals mostly occurs as homozygous loci in most species, however, odd numbers of ITR sites reflecting a hemizygous state have been reported in both gymnosperm and angiosperm groups. Overall, the presence of ITRs appears to be poor predictors of phylogenetic and taxonomic relatedness at most hierarchical levels. The presence of ITRs and the number of sites are not significantly associated to the number of chromosomes. The longitudinal distribution of ITR sites along the chromosome arms indicates that more than half of the ITR presences are between proximal and terminal locations (49.5%), followed by proximal (29.0%) and centromeric (21.5%) arm regions. Intraspecific variation concerning ITR site number, chromosomal locations, and the differential presence on homologous chromosome pairs has been reported in unrelated groups, even at the population level. This hypervariability and dynamism may have likely been overlooked in many lineages due to the very low sample sizes often used in cytogenetic studies.