Karyotype analysis in Bignonieae (Bignoniaceae): chromosome numbers and heterochromatin

ABSTRACT Chromosome numbers and heterochromatin banding pattern variability have been shown to be useful for taxonomic and evolutionary studies of different plant taxa. Bignonieae is the largest tribe of Bignoniaceae, composed mostly by woody climber species whose taxonomies are quite complicated. We reviewed and added new data concerning chromosome numbers in Bignonieae and performed the first analyses of heterochromatin banding patterns in that tribe based on the fluorochromes chromomycin A3 (CMA) and 4’-6-diamidino-2-phenylindole (DAPI). We confirmed the predominant diploid number 2n = 40, as well as variations reported in the literature (dysploidy in Mansoa [2n = 38] and polyploidy in Dolichandra ungis-cati [2n = 80] and Pyrostegia venusta [2n = 80]). We also found a new cytotype for the genus Anemopaegma (Anemopaegma citrinum, 2n = 60) and provide the first chromosome counts for five species (Adenocalymma divaricatum, Amphilophium scabriusculum, Fridericia limae, F. subverticillata, and Xylophragma myrianthum). Heterochromatin analyses revealed only GC-rich regions, with six different arrangements of those bands. The A-type (one large and distal telomeric band) were the most common, although the presence and combinations of the other types appear to be the most promising for taxonomic studies.摘要 染色体数目与异染色质带型变异已被证实可用于不同植物类群的分类学与进化研究。黄钟花族（Bignonieae）是紫葳科（Bignoniaceae）最大的族，其类群多为木质藤本，分类学问题较为复杂。本研究梳理并补充了黄钟花族的染色体数目新数据，并基于荧光染料色霉素A3（chromomycin A3, CMA）与4',6-二脒基-2-苯基吲哚（DAPI）首次开展了该族的异染色质带型分析。 本研究确认黄钟花族以2n=40为主要二倍体染色体数目，同时验证了文献中已报道的变异类型：Mansoa属存在非整倍性（2n=38），Dolichandra ungis-cati与Pyrostegia venusta存在多倍性（2n=80）。此外，我们发现了Anemopaegma属的一种新细胞型（Anemopaegma citrinum，2n=60），并首次报道了5个物种的染色体计数：Adenocalymma divaricatum、Amphilophium scabriusculum、Fridericia limae、F. subverticillata及Xylophragma myrianthum。 异染色质分析仅检测到GC富集区域，共存在6种不同的带型排列。其中A型带（1条大型远端端粒带）最为常见，但其余类型的存在与否及其组合模式在分类学研究中最具应用潜力。