植物细胞显微染色照片，气孔清晰可见
作为植物叶子表皮组织与大气之间交换二氧化碳的门户，气孔是植物生理中的关键要素。因此，它们也是植物的遗传及环境调控的焦点，但此前一直没有发现气孔发育的正信号作用因子。现在，一种具有气孔诱导性质的蛋白已在拟南芥中被发现。
该蛋白被称为“气孔蛋白”（Stomagen），它是一种富含半胱氨酸的肽，见于新叶子内组织（叶肉）层中，在那里它可能通过与细胞表面受体TMM结合来起动气孔细胞系的形成。这一发现提出一个可能性：“气孔蛋白”也许可用来培育具有高气孔密度、从而具有高二氧化碳吸收容量的作物和树木――不仅可以通过基因工程方法来培育，而且可通过喷洒合成“气孔蛋白”或相关合成肽的方法来培育。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 463, 241-244 (14 January 2010) | doi:10.1038/nature08682
Stomagen positively regulates stomatal density in Arabidopsis
Shigeo S. Sugano1,4, Tomoo Shimada1,4, Yu Imai1, Katsuya Okawa2, Atsushi Tamai3, Masashi Mori3 " Ikuko Hara-Nishimura1
1 Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
2 Innovative Drug Research Laboratories, Kyowa Hakko Kirin Co., Ltd., Taksasaki 370-1295, Japan
3 Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, Nonoichi-machi, Ishikawa 921-8836, Japan
4 These authors contributed equally to this work.
5 Correspondence to: Ikuko Hara-Nishimura1 Correspondence and requests for materials should be addressed to I.H.-N.
Stomata in the epidermal tissues of leaves are valves through which passes CO2, and as such they influence the global carbon cycle1. The two-dimensional pattern and density of stomata in the leaf epidermis are genetically and environmentally regulated to optimize gas exchange2. Two putative intercellular signalling factors, EPF1 and EPF2, function as negative regulators of stomatal development in Arabidopsis, possibly by interacting with the receptor-like protein TMM3, 4, 5, 6. One or more positive intercellular signalling factors are assumed to be involved in stomatal development, but their identities are unknown7. Here we show that a novel secretory peptide, which we designate as stomagen, is a positive intercellular signalling factor that is conserved among vascular plants. Stomagen is a 45-amino--rich peptide that is generated from a 102-amino-acid precursor protein designated as STOMAGEN. Both an in planta analysis and a semi-in-vitro analysis with recombinant and chemically synthesized stomagen peptides showed that stomagen has stomata-inducing activity in a dose-dependent manner. A genetic analysis showed that TMM is epistatic to STOMAGEN (At4g12970), suggesting that stomatal development is finely regulated by competitive binding of positive and negative regulators to the same receptor. Notably, STOMAGEN is expressed in inner tissues (the mesophyll) of immature leaves but not in the epidermal tissues where stomata develop. This study provides evidence of a mesophyll-derived positive regulator of stomatal density. Our findings provide a conceptual advancement in understanding stomatal development: inner photosynthetic tissues optimize their function by regulating stomatal density in the epidermis for efficient uptake of CO2.
