Heterochromatin and numeric chromosome evolution in Bignoniaceae, with emphasis on the Neotropical clade Tabebuia alliance

Abstract

Bignoniaceae is a diverse family composed of 840 species with Pantropical distribution. The chromosome number 2n = 40 is predominant in most species of the family, with n = 20 formerly being considered the haploid base number. We discuss here the haploid base number of Bignoniaceae and examine heterochromatin distributions revealed by CMA/DAPI fluorochromes in the Tabebuia alliance, as well as in some species of the Bignonieae, Tecomeae, and Jacarandeae tribes. When comparing the chromosome records and the phylogenies of Bignoniaceae it can be deduced that the base number of Bignoniaceae is probably n = 18, followed by an ascendant dysploidy (n = 18 ® n = 20) in the most derived and diverse clades. The predominant heterochromatin banding patterns in the Tabebuia alliance were found to be two terminal CMA + bands or two terminal and two proximal CMA + bands. The banding pattern in the Tabebuia alliance clade was more variable than seen in Jacarandeae, but less variable than Bignonieae. Despite the intermediate level of variation observed, heterochromatin banding patterns offer a promising tool for distinguishing species, especially in the morphologically complex genus Handroanthus.

Cytogenetics of Four Common Shrub Species of the Mexican Xerophile Scrub in the Mezquital Valley, Hidalgo, Mexico

“…1C, 2C). These karyotypes confirm the predominance of m chromosomes, the scarcity of sm chromosomes, and the rarity of st chromosomes, in addition, the chromosome sizes (Table 2) corroborate the existence of very small chromosomes in this family (Piazzano et al 2015, Cordeiro et al 2020.…”

“…In T. stans (2n=36) the karyotype formula 14m+ 3sm+ 1st sat described differs from that recorded in an Argentine population (14m+ 4sm) whose chromosomes did not carry satellite (Piazzano et al 2015). However, it coincides with that described in a Brazilian populationbased on heterochromatin distribution pattern, in particular with the presence of two chromosomes with long telomeric CMA + bands probably associated with nucleolar organizer regions on a pair of chromosomes of intermediate size (Cordeiro et al 2020). The Mexican population presents secondary constrictions associated with satellites in a pair of SAT chromosomes of similar size (Figs.…”

Variations in heterochromatin content reveal important polymorphisms for studies of genetic improvement in garlic (Allium sativum L.)

“…Chromosomal analysis has been extensively used for the karyotypic characterisation of different groups of plants, allowing the understanding of phylogenetic relationships and the detection of genetic diversity among taxa. Information such as chromosome number and size, morphology, and heterochromatin distribution, among other characteristics, is important for this type of study (Martins et al, 2018;Cordeiro et al, 2020;Querino et al, 2020). It is known that the genus Allium exhibits variation in regards to the chromosome number of its members and wide plasticity in base chromosome number, with reports of x = 7, 8, 10 and 11 (Xie-Kui et al, 2008;Khar et al, 2020).…”