Probing the floral developmental stages, bisexuality and sex reversions in castor (Ricinus communis L.)

Abstract

Castor (Ricinus communis L) is an ideal model species for sex mechanism studies in monoecious angiosperms, due to wide variations in sex expression. Sex reversion to monoecy in pistillate lines, along with labile sex expression, negatively influences hybrid seed purity. The study focuses on understanding the mechanisms of unisexual flower development, sex reversions and sex variations in castor, using various genotypes with distinct sex expression pattern. Male and female flowers had 8 and 12 developmental stages respectively, were morphologically similar till stage 4, with an intermediate bisexual state and were intermediate between type 1 and type 2 flowers. Pistil abortion was earlier than stamen inhibition. Sex alterations occurred at floral and inflorescence level. While sex-reversion was unidirectional towards maleness via bisexual stage, at high day temperatures (Tmax > 38 °C), femaleness was restored with subsequent drop in temperatures. Temperature existing for 2–3 weeks during floral meristem development, influences sexuality of the flower. We report for first time that unisexuality is preceded by bisexuality in castor flowers which alters with genotype and temperature, and sex reversions as well as high sexual polymorphisms in castor are due to alterations in floral developmental pathways. Differentially expressed (male-abundant or male-specific) genes Short chain dehydrogenase reductase 2a (SDR) and WUSCHEL are possibly involved in sex determination of castor.

Genetic Nature and Role of Environment in Sex Expression and Phenological Characters of Pistillate Lines in Castor (Ricinus communis L.)

“…Sex reversions may be early, late and can occur at lower or higher than quarternary orders of spikes (Shifriss 1960;Gopani et al, 1969). Sex reversion and high sexual polymorphisms in castor are due to temperature dependent alterations in oral developmental pathways (Sujatha et al 2021). Earlier studies have concluded that, the pistillateness in NES type is controlled by homozygous recessive genes (N-type) but contain environment sensitive (temperature > 32 0 C, high diurnal range of temperature, relative humidity, nitrogen, soil depth, age of the plant etc.)…”

Proteomic Analyses of Three Inflorescence Styles of Castor (Ricinus communis L.) at Different Developmental Stages

“…For example, high temperature can induce the male development of plants [9]. Season, temperature, photoperiod, light, age of the plant, nutrient level, vegetative activity, pruning, and plant hormones are examples of environmental and intrinsic elements that have an impact on the expression of sex in castor [6,[10][11][12]. Despite significant advancements, the aforementioned ideas remain vulnerable in the lack of cytological data, and little is known about the molecular mechanisms underlying sex variation and the genes responsible for sex expression in castor.…”