TGMS in Rapeseed (Brassica napus) Resulted in Aberrant Transcriptional Regulation, Asynchronous Microsporocyte Meiosis, Defective Tapetum, and Fused Sexine

Abstract

The thermo-sensitive genic male sterility (TGMS) line SP2S is a spontaneous rapeseed mutation with several traits that are favorable for the production of two-line hybrids. To uncover the key cellular events and genetic regulation associated with TGMS expression, a combined study using cytological observation, transcriptome profiling, and gene expression analysis was conducted for SP2S and its near-isogenic line SP2F grown under warm conditions. Asynchronous microsporocyte meiosis and abnormal tapetal plastids and elaioplasts were demonstrated in the anther of SP2S. The tetrad microspore did not undergo mitosis before the cytoplasm degenerated. Delayed degradation of the tetrad wall, which led to tetrad microspore aggregation, resulted in postponement of sexine (outer layer of pollen exine) formation and sexine fusion in the tetrad. The nexine (foot layer of exine) was also absent. The delay of tetrad wall degradation and abnormality of the exine structure suggested that the defective tapetum lost important functions. Based on transcriptomic comparisons between young flower buds of SP2S and SP2F plants, a total of 465 differentially expressed transcripts (DETs) were identified, including 303 up-regulated DETs and 162 down-regulated DETs in SP2S. Several genes encoding small RNA degrading nuclease 2, small RNA 2′-O-methyltransferase, thioredoxin reductase 2, regulatory subunit A alpha isoform of serine/threonine-protein phosphatase 2A, glycine rich protein 1A, transcription factor bHLH25, leucine-rich repeat receptor kinase At3g14840 like, and fasciclin-like arabinogalactan proteins FLA19 and FLA20 were greatly depressed in SP2S. Interestingly, a POLLENLESS3-LIKE 2 gene encoding the Arabidopsis MS5 homologous protein, which is necessary for microsporocyte meiosis, was down-regulated in SP2S. Other genes that were up-regulated in SP2S encoded glucanase A6, ethylene-responsive transcription factor 1A-like, pollen-specific SF3, stress-associated endoplasmic reticulum protein 2, WRKY transcription factors and pentatricopeptide repeat (PPR) protein At1g07590. The tapetum-development-related genes, including BnEMS1, BnDYT1, and BnAMS, were slightly up-regulated in 3-mm-long flower buds or their anthers, and their downstream genes, BnMS1 and BnMYB80, which affect callose dissolution and exine formation, were greatly up-regulated in SP2S. This aberrant genetic regulation corresponded well with the cytological abnormalities. The results suggested that expression of TGMS associates with complex transcriptional regulation.

Protoplast Technology and Somatic Hybridisation in the Family Apiaceae

“…EGMS plays a crucial role in selection of male sterility dependent on sensitivity and adaption to the environmental factors such as high or low temperature, humidity and photoperiod [6]. In a rapeseed TGMS (thermosensitive genic male sterile) line, a temperature above 20 • C resulted in an alteration of gene expression due to a defect of homologous pairing in meiosis I [7].…”

Physiological and Transcriptomic Responses of Antioxidant System and Nitrogen Metabolism in Tomato Roots Treated With Nitrogen Starvation and Re-Supply

“…Nitrogen (N) is an extremely important and necessary macronutrient for plant growth, which is also the main component of nucleic acids, proteins, enzymes, and chlorophyll. N has an important role in plant physiological metabolism and growth, and its supply will directly affect plant growth and the accumulation of secondary metabolites (Liu et al 2017). N containing fertilizers are applied to all important agronomic and horticultural crops to ful ll their requirement, however, only 30-40 % of that fertilizers are utilized by the crops, while the rest of N is lost through leaching or volatilization and causes environmental pollution along with loss of resources (Curci et al 2017;Xin et al 2019).…”

Cytological observation of anther structure and genetic investigation of a thermo-sensitive genic male sterile line 373S in Brassica napus L

“…The previously reported P/TGMS lines in B. napus could be classified into two types, namely, TGMS and PTGMS. The first type includes Xiangyou 91S and its derivative Xiangyou 402S [9,10], 373S [11,12], 104S [13], 160S [14], Huiyou 50S [15,16], SP2S [7,17], 100S [18], and TE5A [19]. The second type comprises H90S [20], N196S [21] and 501-8S [22,23].…”