Progesterone and androstenedione involved in plant growth.
Sex hormones are steroid hormones
that interact with vertebrate androgen or estrogen receptors. They have
been found as messengers to promote the maturation of sexual organs, the
development of secondary sex characteristics, regulation on pain
perception and maintain sexual function (Bińkowska, & Woroń, 2015).
Various forms of estrogen derivatives have been widely used in
contraception, treatment of menopausal syndrome in women, prostatic
hypertrophy in men and other endocrine disorders (Maurer, Lissounov,
Knezevic, Candido, & Knezevic, 2016).
Progesterone (PROG) is one kind of mammalian gonadal hormone necessary
for the regulation of ovulation and menstruation. It is now detected in
a range of plant species (Tarkowská, 2019). It was reported that the
PROG contained in some plant tissues even exceeded 2600 ng/g (dry
weight) (Iino et al., 2007). Five secondary steroids as the mammalian
gestagen PROG are found in Adonis aleppica and Juglans regia (Tarkowská,
2019; Pauli, Friesen, Gödecke, Farnsworth, & Glodny, 2010). They assume
a variety of physiological functions in plants. For instance, the
Arabidopsis seedlings were found to be promoted by PROG at low
concentrations but suppressed at higher concentrations (Iino et al.,
2007). A similar phenomenon is found in sunflowers. High PROG
concentration (0.25 μg per plant) stimulated the elongation of shoots,
while a lower concentration (0.1 μg per plant) stimulated the growth of
sunflower roots (Bhattacharya, & Gupta, 1981). In addition, PROG can
regulate plant mineral management, including calcium, magnesium,
phosphorus, sulfur, copper and so on (Dumlupinar, Genisel, Erdal,
Korkut, & Taspinar, 2011). Furthermore, it was reported that PROG (1
and 10 μM) induces the flowering in winter wheat. Same as
androstenedione (0.1 μM) in Arabidopsis thaliana which leads to
more than twice as generative percentage compared to control (Janeczko,
Filek, Biesaga-Kościelniak, Marcińska, & Janeczko, 2003). In terms of
environmental resistance, PROG alone (0.1 µmol L−1)
can alleviate cold stress by modulation of mitochondrial respiratory
pathway (Erdal, & Genisel, 2016). Potential role of PROG in response to
oxidative damage (10−6 M) is demonstrated by influence
oxidative enzymes such as SOD, POX and CAT (Erdal, & Dumlupinar, 2011).
The androstenedione (AN) is another common sex hormone precursor in both
sexes and takes charge of the biosynthesis of testosterone (Haring et
al., 2012). New result demonstrated the effect of androstenedione (1 µM)
on winter wheat exposed to low temperature (Janeczko et al., 2018). A
key role for AN is to mitigate damages caused by freezing temperatures
and enhance frost resistance in wheat. Moreover, there has been found an
interaction between animal hormone and plant hormone in wheat. AN
triggers an accelerated generative development of wheat via increasing
GA3 and cytokinins (Janeczko et al., 2018). The frost
resistance increases in the process due to AN-induced changes in redox
homeostasis. In addition, AN regulates enzyme activity including
superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), polyphenol
oxidase (PPO) and alpha-amylase against oxidative damage in endosperm of
maize seeds (Erdal, 2012). Androstenedione can alleviate drought stress
and compensate efficiency of photosystem II in soybean by possible
effect on aquaporin functionality and membrane stability (Janeczko,
Kocurek, & Marcińska, 2012). These studies provide new insights into AN
as a novel plant growth regulator to improve resistance in crop.
Furthermore, the ability of plants to convert sterols into steroid
hormones is found, involving progesterone, testosterone,
androstadienedione, androstenedione, and estrogens. This means that
plants have endogenous steroid hormones just like animals. However, the
biological activity of these hormones remains to be explored (Tarkowská,
2019).
Oxytocin affects the
production of secondary plant constituent in vitro
Oxytocin is a neuropeptide widely used by medical doctors and
veterinarians (Perry, 2014). Previous review demonstrated its role in
the dynamic function of the social brain, such as result in changes in
brain activity and delivery in pregnant mammals (Perry, 2014; Gordon et
al., 2013). The oxytocin signaling system is ubiquitous across the
animal kingdom.
Oxytocin affects the production of secondary plant constituent in vitro.
The influence of oxytocin (100 μg/L) on biomass accumulation as well as
on the production of glycyrrhizin, a key phytoconstituent of
liquorice used in the pharmaceutical and food industries (Yu et al.,
2017), was observed in the cell cultures of Abrusprecatorius (Karwasara, Tomar, & Dixit, 2011). Moreover, the
article demonstrated the use of oxytocin to increase the growth of
pumpkins and cucumbers in India (None, 2009). However, information about
the function and regulation of oxytocin in planta is still limited.
These would be worthwhile avenues to explore.