Abstract
Rice yield is highly sensitive to increased temperature. Given the trend of increasing global temperatures, this sensitivity to higher temperatures poses a challenge for achieving global food security. Early seed development in rice is highly sensitive to unfavorable environmental conditions. Heat stress (HS) during this stage decreases seed size and fertility, thus reducing yield. Here, we explore the transgenerational phenotypic consequences of HS during early seed development on seed viability, germination, and establishment. To elucidate the impact of HS on the developmental events in post-zygotic rice seeds, we imposed moderate (35°C) and severe (39°C) HS treatments initiated 1 day after fertilization and maintained for 24, 48, or 72 h. The transient HS treatments altered the initiation of endosperm (ED) cellularization, seed size and/or the duration of spikelet ripening. Notably, seeds exposed to 24 and 48 h moderate HS exhibited higher germination rate compared to seeds derived from plants grown under control or severe HS. A short-term HS resulted in altered expression of Gibberellin (GA) and ABA biosynthesis genes during early seed development, and GA and ABA levels and starch content at maturity. The increased germination rate after 24 of moderate HS could be due to altered ABA sensitivity and/or increased starch level. Our findings on the impact of transient HS on hormone homeostasis provide an experimental framework to elucidate the underlying molecular and metabolic pathways.
Highlights
Rice (Oryza sativa L.) is one of the most important crops for global food security
To observe the effects of Heat stress (HS) imposed during early ED development on mature rice seeds, we imposed a moderate (35◦C) and a severe (39◦C) HS for 24, 48, or 72 h initiated at 24 h after fertilization (HAF)
We observed that moderate HS (35◦C) during early seed development significantly reduced the final seed size at maturity (Figure 1A)
Summary
Rice (Oryza sativa L.) is one of the most important crops for global food security. Rice is grown under a variety of environments with an estimated planted area of 161 million ha (Seck et al, 2012). Current global climate predictions are expected to negatively impact rice production. It is estimated that increased temperatures will decrease rice production by up to 25% (Wassmann et al, 2009; van Oort and Zwart, 2018). Two major factors causing decline in rice yield are: heat stress (HS) induced sterility and shortening of the growing season (Tao et al, 2008; Li et al, 2015; van Oort and Zwart, 2018)
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