BeMADS1 is a key to delivery MADSs into nucleus in reproductive tissues-De novo characterization of Bambusa edulis transcriptome and study of MADS genes in bamboo floral development

Abstract

BackgroundThe bamboo Bambusa edulis has a long juvenile phase in situ, but can be induced to flower during in vitro tissue culture, providing a readily available source of material for studies on reproductive biology and flowering. In this report, in vitro-derived reproductive and vegetative materials of B. edulis were harvested and used to generate transcriptome databases by use of two sequencing platforms: Illumina and 454. Combination of the two datasets resulted in high transcriptome quality and increased length of the sequence reads. In plants, many MADS genes control flower development, and the ABCDE model has been developed to explain how the genes function together to create the different whorls within a flower.ResultsAs a case study, published floral development-related OsMADS proteins from rice were used to search the B. edulis transcriptome datasets, identifying 16 B. edulis MADS (BeMADS). The BeMADS gene expression levels were determined qRT-PCR and in situ hybridization. Most BeMADS genes were highly expressed in flowers, with the exception of BeMADS34. The expression patterns of these genes were most similar to the rice homologs, except BeMADS18 and BeMADS34, and were highly similar to the floral development ABCDE model in rice. Transient expression of MADS-GFP proteins showed that only BeMADS1 entered leaf nucleus. BeMADS18, BeMADS4, and BeMADS1 were located in the lemma nucleus. When co-transformed with BeMADS1, BeMADS15, 16, 13, 21, 6, and 7 translocated to nucleus in lemmas, indicating that BeMADS1 is a key factor for subcellular localization of other BeMADS.ConclusionOur study provides abundant B. edulis transcriptome data and offers comprehensive sequence resources. The results, molecular materials and overall strategy reported here can be used for future gene identification and for further reproductive studies in the economically important crop of bamboo.

Flowering of Woody Bamboo in Tissue Culture Systems

“…The gene structures and amino acid sequences were highly similar to rice MADS homologs (77–92%). Most importantly, all of the predicted proteins contain M, I, K, and C domains, definitive of type II MADS (Shih et al, 2014). When the whole genome of moso bamboo was published (Peng et al, 2013), 34 MADS genes were identified (Peng et al, 2013; Cheng et al, 2017).…”

“…Five genes did not have the M domain (PheMADS56-4, PheMADS21, PheMADS14, PheMADS29, and PheMADS90; Cheng et al, 2017), while others were very short and contained only the M domain (PheMADS1, PheMADS5, PheMADS64, PheMADS65; Cheng et al, 2017). Thus far it is unknown whether these differences are due to the starting materials (DNA from in vivo flowers in Cheng et al, 2017 vs. RNA from in vitro flowers in Shih et al, 2014). …”

“…However, most fluorescently tagged BeMADS proteins cannot enter the nucleus when expressed in either Arabidopsis protoplasts or in bamboo leaves, but can when expressed in lemmas (Shih et al, 2014). This indicated that correct results can only be shown in the correct materials.…”

“…Arabidopsis ) gives misleading results for bamboo (Shih et al, 2014). While many bamboo flower-related genes have been identified via genomics, the mechanisms of flowering, the expression of floral genes and proteins, and other functional analyses must be done in bamboo reproductive tissues.…”

Bamboo Flowering from the Perspective of Comparative Genomics and Transcriptomics

“…In comparison, the molecular aspects of bamboo flowering remain at a nascent stage. Studies have been conducted to characterize a limited number of flowering genes in different bamboo species such as MADS18 from Dendrocalamus latiflorus (Bo et al, 2005), FLOWERING LOCUS T (FT) from P. meyeri (Hisamoto et al, 2008), TERMINAL FLOWER 1 (TFL1) like gene from Bambusa oldhamii (Zeng et al, 2015), FRIGIDA (FRI) from P. violascens (Liu et al, 2015), MADS1 and MADS2 from P. praecox (Lin et al, 2009), 10 genes related to floral transition and meristem identity in D. latiflorus (Wang et al, 2014) and 16 MADS box genes from B. edulis (Shih et al, 2014). Such targeted approaches are being complemented by high-throughput approaches, namely, de novo transcriptome sequencing and suppression subtractive hybridization (Lin et al, 2010; Liu et al, 2012; Zhang et al, 2012; Peng et al, 2013; Gao et al, 2014; Ge et al, 2016; Wysocki et al, 2016; Zhao et al, 2016).…”