Figure 1.

Transcriptomes of pollen at different stages of development and germination in Arabidopsis. Inside the anther, meiosis of the microspore mother cell produces four uninucleate microspores (UNMs). Each microspore divides to give a BCP containing a large vegetative cell (nucleus in gray) and a small generative cell (blue). Division of the generative cell produces two sperm cells (blue) in the TCP. TCP develops to an MP (or dry). On germination medium, MP becomes HP, and a tube emerges in about 1 h and elongates in 4–5 h. SIV PTs refer to tubes grown through the pistil (pink) and emerged from the cut style onto a medium (scale reduced). Transcriptomes analyzed here are from three studies. Pollen stages UNM, BCP, TCP, and MP are from Honys and Twell (2004); MP, HP, and PT 4 h in vitro are from Wang et al. (2008), and dry, PT 0.5 h, PT 4 h, and SIV are from Qin et al. (2009). Transcriptome after heat stress is from two reports. In (1), whole plants were exposed to diurnal heat/cold (orange/blue bars) cycles for 7 d before anthesis. Each cycle was designed with 18 h at cool temperature (10°C) and a 6-h period in which temperatures were ramped up and down with 40°C mid-day peak for 1 h. MP RNA was analyzed (Rahmati Ishka et al., 2018). In (2), MP on germination medium was given 35°C (orange bar) or 24°C for 5 h before RNA was isolated (Poidevin et al., 2020).