Abstract
Gravity is an important ecological factor regulating plant growth and developmental processes. Here we used various molecular and biochemical approaches to investigate artificial and normal gravistimulation’s effect on the early growth stages of rice (Oryza sativa L.) by changing the orientations of Petri dishes. Rate of amino acid formation, root and shoot growth, and OsPIN expression was significantly higher under gravistimulation compared with the control. Clinostat rotation positively affected plant growth and amino acid profile. However, under normal gravity, vertical-oriented seedlings showed high amino acid levels compared with clinostat, 90°-rotated, and control seedlings. Similarly, seedling growth significantly increased with 90°-rotated and vertical orientations. Artificial gravity and exogenous indole-3-acetic acid induced OsPIN1 expression in the roots, root shoot junction, and shoots of clinorotated seedlings. Phenyl acetic acid induced OsPIN1 expression in the roots and root shoot junction of clinorotated seedlings but not in the shoot. The current study suggests that OsPIN1 is differentially regulated and that it might be involved in the regulation of plant growth. Conversely, OsPIN2 and OsPIN3a are gravity sensors and highly induced in the roots and root shoot junctions of vertical and 90°-rotated seedlings and play an important role in stress conditions. Thus, on exposure to gravity, hormones, and UV-C radiation, these genes are highly regulated by jasmonic acid, 6-benzylaminopurine and gibberellic acid.
Highlights
Microgravity conditions impact biological processes such as graviperception and graviresponses
We identified a high expression of OsPIN3a and OsPIN2 in the roots, root shoot junction, and shoot of rice seedling under normal gravity stimulation
We examined the effect of UV-C radiation, exogenously applied phytohormones, and gravistimulation on OsPIN1, OsPIN2, and OsPIN3a genes in rice
Summary
Microgravity conditions impact biological processes such as graviperception and graviresponses. Free-fall or parabolic flight can generate microgravity conditions, these methods do not provide sufficient time for researchers to study most morphogenetic and growth phenomena of plants. In this context, ground-based clinostats are instrumental. Indole-3-acetic acid (IAA), the main auxin in higher plants, maintains various developmental processes of plants, including growth direction, root and shoot branching, and vascular differentiation[14,15]. (PIN) efflux carrier proteins are plant-specific auxin transporters that play an important role in polar auxin transport and in establishing IAA concentration gradients[18]. Nagdong) to test the hypothesis that microgravity and normal gravity differentially affect gene expression, amino acid profile, morphogenesis, and early stage plant growth. The principal objective was to gain a better understanding of plant growth under altered gravity simulation on the ground and guide future space experiments (i.e., under real microgravity conditions)
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