Cytological behaviour of floral organs and in silico characterization of differentially expressed transcript-derived fragments associated with ‘floral bud distortion’ in soybean

Abstract

An attempt was made to understand the 'floral bud distortion' (FBD), an unexplored disorder prevailing in soybean. Cytological behaviour of floral reproductive organs and in silico characterization of differentially expressed transcript-derived fragments (TDFs) in symptomatic and asymptomatic soybean plants were carried out. Pollens in asymptomatic plants do not have defects in number, size, shape and function. However, in symptomatic plant, pollens were found nonviable, abnormal in shape and with reduced germination ability. Here, we employed a computational approach, exploring invaluable resources. The tissue-specific transcript profile of symptomatic and asymptomatic sources was compared to determine differentially expressed TDFs associated with FBD to improve its basic understanding. A total of 60 decamer primers produced 197 scorable amplicons, ranged 162-1130 bp, of which 171 were monomorphic and 26 were differentially regulated. Reproducible TDFs were sequenced and characterized for their homology analysis, annotation, protein-protein interaction, subcellular localization and their physical mapping. Homology-based annotation of TDFs in soybean revealed presence of two characterized and seven uncharacterized hits. Annotation of characterized sequences showed presence of genes, namely auxin response factor 9 (ARF9) and forkhead-associated (FHA) domain, which are directly involved in plant development through various pathways, such as hormonal regulation, plant morphology, embryogenesis and DNA repair.

Transcriptomic signature reveals mechanism of flower bud distortion in witches’-broom disease of soybean (Glycine max)

“…Auxin-responsive promoter elements are known to be involved in switching of vegetative to reproductive phase along with environmental signalling. Phytoplasma perturbs this normal reproductive development of floral tissue leading to FBD [12].…”

“…The geographical situation is 20.42°N latitude and 77.02°E longitude with medium black, with clay, fairly levelled and uniform in topography with appropriate drainage. To discriminate symptomatic and asymptomatic plants, pollen viability, morphology by simple and scanning electron microscope (SEM), stigma receptivity assay, anther morphology and germination assay was done at R2 reproductive stage as previously described [12].…”

“…According to the earlier reports, several biotic factors have been identified in the host leading to reduced pollen vigour [7], seed mass variants [8], floral abnormalities, sepal hypertrophy, virescence, phyllody, aborted reproductive organs [9], enhanced vegetative growth [10], premature flower abortion [11], etc. Cytological examination of plant reproductive organs revealed distorted pollen grains in the symptomatic plants hampering pollination and fertilization [12].…”

“…The symptoms are also not predictable. Abnormal development in the floral bud formation in witches’-Broom Disease of soybean causes, even acute loss in productivity [12]. It is referred in India as ‘floral bud distortion’ caused by phytoplasma [14, 15].…”

“…Though RNA-Seq atlas of soybean has 14 diversified tissues including flower but no expression data is available for any abiotic and biotic stresses [20, 21]. Cytological and limited molecular study on FBD has been carried out revealing 27 DEG having ARF9 transcriptional factor and a regulatory protein FHA along with their protein-protein interaction network [12]. Though whole genome sequence of soybean has been done in 2010 [22] but without RNA-Seq approach detailed mechanism of FBD cannot be deciphered.…”